Here, try this! I'm sure there are better ways to code a program like this but I am also a newb so this is the best I could do with my knowledge so far.

rem Calculation Program 2.0
rem Made By : Ben Smerglia
rem First, I need to find out what the user wants to do.
Decision:
Input "Do you want to add, subtract, multiply, or divide? Input is case sensitive! ",userChoice$
If userChoice$="add" then Gosub Add
If userChoice$="subtract" then Gosub Subtract
If userChoice$="multiply" then Gosub Multiply
If userChoice$="divide" then Gosub Divide
rem Addition
Add:
Input "Type Value 1: ",a#
Input "Type Value 2: ",b#
c#=a#+b#
Print C#
Suspend For Key
Cls
Gosub Decision
rem Subtraction
Subtract:
Input "Type Value 1: ",a#
Input "Type Value 2: ",b#
c#=a#-b#
Print C#
Suspend For Key
Cls
Gosub Decision
rem Multiplication
Multiply:
Input "Type Value 1: ",a#
Input "Type Value 2: ",b#
c#=a#*b#
Print C#
Suspend For Key
Cls
Gosub Decision
rem Division
Divide:
Input "Type Value 1: ",a#
Input "Type Value 2: ",b#
c#=a#/b#
Print C#
Suspend For Key
Cls
Gosub Decision

Wether that's 20 lines or not, idk, but I'm just showing the nerd something...

Member of Bee Hive Studios | freewebs.com/beehivestudios

Currently developing: 3D PacMan (tentative title)