4b+6= 2 - b + 4 (combine terms: 2 + 4 = 6) 4b + 6 = 6 - b (add the b to the other side to get rid of the negative) 5b + 6 = 6 (subtract 6 from one side to the other) 5b = 0 (divide by 5 on both sides) b = 0
Firstly, you do 90 - 42 to get the amount of brownies sold, which is 48. Then, you put 42 and 48 into a ratio like 42:48. After that, all you need to do is simplify to get 7:8.