Sub CombineValues()
Dim i As Long
With ActiveSheet
  For i = 1 To .Cells.SpecialCells(xlCellTypeLastCell).Row
    If IsNumeric(Evaluate(.Range("A" & i).Value)) And IsNumeric(Evaluate(.Range("B" & i).Value)) Then
      .Range("B" & i).Value = Evaluate(.Range("A" & i).Value) + Evaluate(.Range("B" & i).Value)
    Else
      .Range("B" & i).Value = .Range("A" & i).Value & " " & .Range("B" & i).Value
    End If
      .Range("B" & i).NumberFormat = "General"
  Next
End With
End Sub