Question 128
We know that velocity is V = a+bt, where a is a constant and t is the variable. 

When t = 0,  a+b*0 = 20
When t = 11, a+b*11 = 53

This is a simple linear system, which you can solve using a linear system solver that will show work. The solution is pretty obvious, the first equation gives you a=20, and the second equation b*11 = 33, gives you b = 11.