Question

Suppose for any positive integer n, s(n) is the remainder when n is divided by 19. Find the number of pairs of integers (a,b), such that 1≤a≤b≤18, and for all k=1,2,...,18
k+s(ka)+s(kb)≥20

Answer 1

*

Answer 2

thank dude that helped a lot

Answer 3

sorry i mean *bookmark :)