Amusic store gives away every 20th customer a $5 gift card every 50th customer gets a $10 gift card which customer will be the first to receive both gift cards

U need to find the common multiple, for 20 and 50. The common multiple is 20 and 50 as 100 can be divided by both, 100/50 is 2 and 100/20 is 5. 

so the 100th customer will be the first the receive both gift card.

Im not that good with division but i think 5 is -6but dont quote me on thatim not the best in division but thats my answer