if the average ( arithmetic mean ) of a and b is 45 and the average of b and c is 70 , what is the value of c − a ?
"the arithmetic mean of a and b = ( a + b ) / 2 = 45 - - a + b = 90 - - 1 similarly for b + c = 140 - - 2 subtracting 1 from 2 we have c - a = 50 ; answer : b"
subtract(multiply(70, const_2), multiply(45, const_2))