I haven't started learning variables, and stuff like that yet in class, and I wanna be ahead, so can somebody teach me?

Hey, so in this case, the variable are t and u.
They gave you the numbers that each variable represents. Which are:
t=6 and u=1/4
So now what you need to do is, replace the variables with the numbers they represent in the equation. So it’s gonna be:
6(6)-20-32(1/4)
So now use PEMDAS to calculate. PEMDAS (parentheses - exponents - multiplication - decision - addition - subtraction)

So multiply 6 with 6, and then multiple 32 with 1/4.
36-20-8
Now subtract to get the answer.

36-20-8= 8

The answer is 8