Normally when you want to delete rows from a worksheet you would create a simple loop that would check if a row should be deleted or not, and then delete each row separately. This works fine as long as you have a small data set or don't have to delete many rows.

Sub DeleteRowsExample()
' may be slow on large data sets, multiple delete operations
Dim r As Long, i As Long
    i = 0
    With Range("A5").CurrentRegion
        For r = .Rows.Count To 1 Step -1
            If .Cells(r, .Columns.Count).Value < 10000 Then
                .Rows(r).EntireRow.Delete
                i = i + 1
            End If
        Next r
    End With
    MsgBox i & " rows deleted!", vbInformation
End Sub

Sub MarkAndDeleteRowsExample()
' fast on large data sets, only one delete operation
Dim frn As Long, fcn As Long, lrn As Long, lcn As Long
Dim blnDelete As Boolean, lngCount As Long, r As Long
    With Application
        .ScreenUpdating = False
        .Cursor = xlWait
        .Calculation = xlCalculationManual
        .StatusBar = "Please wait..."
    End With
    With Range("A1").CurrentRegion
        frn = .Row
        fcn = .Column
        lrn = frn + .Rows.Count - 1
        lcn = fcn + .Columns.Count - 1
    End With
    Cells(frn, lcn + 1).Formula = "Delete Row?" ' add temporary column caption
    For r = frn + 1 To lrn
        blnDelete = False
        On Error Resume Next
        blnDelete = Range("A" & r).Value < 10000 ' do some validation
        On Error GoTo 0
        Cells(r, lcn + 1).Formula = blnDelete ' add row delete flag
        If blnDelete Then
            lngCount = lngCount + 1 ' count rows to delete
        End If
    Next r
    If lngCount > 0 Then ' found 1 or more rows to delete
        lngCount = QuickDeleteRows(Range("A1").CurrentRegion)
    End If
    Cells(frn, lcn + 1).ClearContents ' remove temporary column caption
    With Application
        .StatusBar = False
        .Calculation = xlCalculationAutomatic
        .Cursor = xlDefault
        .ScreenUpdating = True
    End With
    MsgBox lngCount & " rows deleted!", vbInformation
End Sub

Function QuickDeleteRows(objRange As Range, Optional blnHeader As Boolean = True, _
    Optional blnDeleteEntireRow As Boolean = True) As Long
' the last column in objRange must be populated with True or False, rows containing True will be deleted
Dim r As Long, c As Long, i As Long, lngCount As Long
    QuickDeleteRows = 0 ' count of deleted rows
    If objRange Is Nothing Then Exit Function
    
    With objRange
        If .Parent.ProtectContents Then Exit Function ' the worksheet is protected
        r = .Rows.Count: c = .Columns.Count
        If r < 2 Or c < 2 Then Exit Function

        lngCount = 0 ' count of deleted rows
        ' sort objRange based on the last columns content, rows containing True will end up last in the range
        If blnHeader Then
            .Sort Key1:=.Cells(2, c), Order1:=xlAscending, Header:=xlYes
        Else
            .Sort Key1:=.Cells(1, c), Order1:=xlAscending, Header:=xlNo
        End If
        ' find the first row with True in the last column of objRange
        i = 0
        On Error Resume Next
        i = Application.WorksheetFunction.Match(True, .Columns(c), 0)
        On Error GoTo 0
        If i > 0 Then
            On Error Resume Next
            If blnDeleteEntireRow Then ' delete the entire worksheet row
                .Range(.Cells(i, 1), .Cells(r, c)).EntireRow.Delete
            Else ' delete the rows in objRange only, shift cells below up
                .Range(.Cells(i, 1), .Cells(r, c)).Delete xlShiftUp
            End If
            On Error GoTo 0
            lngCount = r - .Rows.Count ' count of deleted rows (original - current rows count)
        End If
    End With
    QuickDeleteRows = lngCount
End Function