(45+30)-x=12 y-9×5=35 (90+x)-4×10=60

(45+30)-x=12 75 - x = 12x = 75 - 12x = 63y-9×5=35 y - 45 = 35y = 35 + 45y = 80(90+x)-4×10=6090 + x - 40 = 6050 + x = 60x = 60 - 50x = 10