Jenny baked some cheese and banana muffins in the ratio of 2: 3

After selling a total of 84 cheese and banana muffins, the ratio of cheese
and banana muffins became 1 : 5. If there were 155 banana muffins finally
how many cheese muffins were sold?

c/b = 2/3, so b = 3/2 c

If x cheese muffins were sold, then
(c-x)/155 = 1/5
c-x = 31
x = c-31

3/2 c - (84-(c-31)) = 155
c = 108
so b = 162
so 108-31 = 77 cheese muffins were sold
and 7 banana muffins were sold.
check: (108-77)/(162-7) = 31/155 = 1/5 ✅