if a : b = 4 : 1 , then find ( a - 3 b ) / ( 2 a - b ) ?
answer : option b a / b = 4 / 1 = > a = 4 b ( a - 3 b ) / ( 2 a - b ) = ( 4 b - 3 b ) / ( 8 b - b ) = b / 7 b = > 1 / 7
divide(subtract(4, 3), subtract(multiply(2, 4), 1))