the best way to tackle these is to learn how to write them without congruences. that is, if you are unfamiliar with manipulating congruences themselves. when you have a set of equations working with, it is usually easier to "see" what you need to do. write out what the statements mean and then write out what you want to show.

the problem asked you to prove

, where

so

means

for

(i suppose you know how to get to this equation)

you are required to use the equation above to show that

that is, you want to show

for some

since

, we can get the desired result by dividing the first equation through by

and simplifying