What is the system of solution x+y=18 and y=-4x

First, we need to figure out y. Y has to be 4 times smaller than x. Y cannot be a decimal, and y cannot exceed 3. If x is 24, negative 4 x would be - 96. Y would be - 96, and - 96 plus 24 is - 72. So we need x to be smaller. if x is