What is 10 x -38 mod 11?
What is 16 x -80 mod 16?
What is 278-421 mod 19?
No it is indeed $\displaystyle 17$ for the last one, because $\displaystyle 278 \equiv 12 \ \ \ \ [19]$ and $\displaystyle -421 \equiv -3 \ \ \ \ [19]$.
EDIT : ah yes chiph588@ you are right, but why put a substraction question following two multiplication questions ? This is confusing