Help if d is GCD(greatest common divisor)
and d(x;y) where x and y are natural numbers
is d(x+y;xy)-d(x;y) an odd or an even number?

Jake bakes and sell apple pies. he sells each pie for $5.75 . the materials to make the pies cost $40. the boxes jake puts the pies in cost & 12.50 total. how many pies does jake need to sell to earn a profit of $50