5y 4 2y 9 July 8, 2019 16 32 64 128 9 5y 4 2y 5 3x 5y 4 9x 2y 7 by substitution method 3x 5y 4 9x 2y 7 3x 5y 4 9x 2y 15y 4 2y 9 5y 6 0 3x 5y 4 0 9x 2y 1