There are some macarons in a box. The macarons can be put into plates of 5 or 10 with no macarons leftover. When the macarons are put into plates of 13, there are short of 6 macarons on the last plate. If there are more than 20 macarons but less than 40 macarons, how many macarons are there in the box?
If macarons can be put into plates of 5 or 10 with no macarons leftover, the number of macarons is a multiple of 10 as 10 is a multiple of 5.

Multiples of 10 that are greater than 20 but less than 40: 20, 30, 40

Multiples of 13 that are greater than 20 but less than 40: 26, 39
Multiples of 13 (- 6) that are greater than 20 but less than 40: 20, 33

Common number = 20

Number of macarons = 20

Answer(s): 20