3 задание. . . . . .......
370-320+150-90 320+50-60+70
1) (370-320)+(150-90)=50+60=110 2)(320+50)-(60+70)=370-110=260 3)(620+30)-(670-50)=650-620=30 4)(780-720)+(960-560)=60+500=560