If$a≡16(mod37)$and$b≡21(mod37)$,thenforwhatinteger$n$intheset${0,1,2,…,35,36}$isittruethat$$a−b≡n(mod37) ?$$
a mod 37 = 16 b mod 37 = 21 (a - b) mod 37 = n, solve for n
a = 16 and b = 21 (a - b) mod 37 = n
(16 - 21) mod 37 = - 5
n =37 + (-5) = 32
+223 
