For every 3 packages that Marcella wraps, she uses 12 of a roll of wrapping paper.If she uses 2/12 rolls of wrapping paper, how many packages has she wrapped?

for every 3 packages, she uses 1/2 a roll of wrapping paper

if she uses 2 1/2 rolls.....

(2 1/2) / (1/2) ....* 3
(5/2) / (1/2).....* 3
(5/2 * 2) * 3
5 * 3 =
15 packages <===