Undefined Variable Issues

I'm trying to perform simple arithmatic problems using MathCAD using many different variable names. However, when I try to use a variable like "ALLL" or "Xtotal" MathCAD will highlight the letters or word that is subscripted and say "This variable is undefined" and will not calculate the equation. Is there a way to fix this? Im new to MathCAD, so if anyone has any suggestions I greatly appreciate it. Also, I attached the worksheet I'm working on, so if you have any suggestions as to how to set up my work in a more consice manner I'd greatly appreciate it.

Thank you,

Dan