7y 12 5 3y 15 4 July 8, 2019 16 32 64 128 (7y - 5)/(12y) - (10y - 19)/(12y) + (10 - 15y)/(12y) 5 + (7y - 12)/3 = y + 13 4 7y-(2 5y+12 4)=1 9