Option Explicit On
Option Strict On
Public Class frmMain

    Private Sub btnConvert_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConvert.Click
        Dim fahrenheitTemp, celsiusTemp As Double

        fahrenheitTemp = CDbl(txtFahrenheit.Text)
        'Function call to FtoC that returns the celsius
        celsiusTemp = FtoC(fahrenheitTemp)
        txtCelsius.Text = CStr(celsiusTemp)
    End Sub

    'Function definition for FtoC
    Function FtoC(ByVal fTemp As Double) As Double
        Return (5 / 9) * (fTemp - 32)
    End Function
End Class