Modular arithmetic congruence class simple proof I have the following question but I'm unsure of how it can be approached by a method of proof. I'm new to modular arithmetic and any information on how to solve this would be great for me.

(b) Let $t,s\in\{0,1,2,3,4,5\}$. In $\mathbb Z_{25}$, prove that $[t]\,[s]\neq[24]$.


Hint $\ $ If $\rm\:a\:|\:b\:$ in $\Bbb Z$ then so too in every ring, and the quotient is unique if $\rm\:a\:$ is not a zero divisor. Also, divisors of units are units, so $\rm\: mod\ 25\:$ the divisors of $\:24\equiv -1\:$ are units, so coprime to $5$.
