Brownie Packs Sold Calculation

During a school fundraiser, the students sold packs of cookies and brownies. Each cookie pack contains c cookies, and each brownie pack contains b brownies. The total number of packs sold was 50, and the number of cookie packs sold was three times the number of brownie packs sold. If the total number of cookies sold was 120, how many brownie packs were sold?

Let the number of brownie packs be represented by b.