i have problem about if else code in my program.
i also have made many changing in this code but still i didn't get the result that i want.

my program is about vending machine.

here is the code:

Private Sub btnpepsi_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnpepsi.Click
        TextBox2.Text = "RM 2.50"
        Dim pepsi As Double
        Dim amount As Double

        If pepsi < 10 Then
            If displayText.Text > TextBox2.Text Then
                amount = displayText.Text - TextBox2.Text
                ListBox1.Items.Add("Your balance: " & amount & ".")
            End If
            TextBox2.Text = "Sold out"
            ListBox1.Items.Add("Sold out")
        End If
    End Sub

First off you need to find which types of variables to use.

You cannot subtract to string as if they were double

You want to create a variable for the cost of the pespi.

dim pepsicost as double= 2.50

TextBox2.Text="RM " & pepsicost

You need to make a function that will how many pepsi you have when you click on the Pepsi button because when you are creating "dim pepsi as double" you just declaring a variable but that variable does not have any value.

So make sure to compare DisplayCost>PepsiCost ...not strings

your variable amount(double) cannot subtract a string with another string and give you a double.

There are many tutorial on Youtube that can help you understand the difference in variable and how to send value over to other functions.

This part code :

If displayText.Text > TextBox2.Text Then ' Line 8
     amount = displayText.Text - TextBox2.Text ' Line 9

Your textbox2 value is String. you cannot subtract or compare it with a double value.
You need to convert it to double.

Exacttly. Text property is a String type. So you cannot use operatoros like <, > on them. YOu can only use these kind of operators on numbers (int, decimal, double, float,.. types).

Dim a As Double = Double.Parse(displayText.Text)
Dim b As Double = Double.Parse(TextBox2.Text)
If a > b Then
	amount = a - b
End If