4x = 5(45 - x) - 9 {four times first is 9 less than five times second}
4x = 225 - 5x - 9 {used distributive property}
4x = -5x + 216 {combined like terms}
9x = 216 {added 5x to both sides}
x = 24 {divided both sides by 9}
45 - x = 21 {substituted 24, in for x, into 45 - x}