10 binders can bind 1400 books in 21 days . how many binders will be required to bind 1800 books in 20 days ?
"binders books days 10 1400 21 x 1600 20 x / 10 = ( 1800 / 1400 ) * ( 21 / 20 ) = > x = 12 answer : e"
divide(divide(1800, 20), divide(1400, multiply(10, 21)))