Check if this example works for you:
Selection.TypeText "How to solve this equation?" & vbCrLf
Dim r As Range
Set r = Selection.Range
r.Text = "1/2 + 1/3"
Selection.Start = r.End + 1
Selection.End = Selection.Start
Selection.OMaths.Add(r).OMaths(1).BuildUp
Selection.TypeText vbCrLf & "First you have to make the denominators equal by extending the fractions"