300 - х*5 = 210 5х = 300 - 210 5х = 90 х = 18 (300 -х) *5 = 210 300 - х = 210 : 5 300 - х = 42 х = 300 - 42 х = 258 (150 - 20)х = 65 х = 65 : 130 х = 1/2 х = 0,5 (х + 4) * 7 = 350 х + 4 = 350 : 7 х + 4 = 50 х = 50 - 4 х = 46