Question

first multiple of 5 and 6 that is exactly divisible by 20

Answer 1

The answer is 60 because it is a multiple of both 5 and 6 and and we know 20×3=60
Whereas if we take 20×2=40 then it will not be a multiple of 6

Answer 2

$5 \times 8 = 40 \div 20 = 2and6 \times 10 = 60 \div 20 = 3$