51. Вычисли.

Решим цепочки вычислений: **А** 1) $13 \cdot (-5) = -65; -65 - 15 = -80; -80 : 20 = -4; -4 + 30 = 26$ 2) $-90 - 70 = -160; -160 : (-4) = 40; 40 \cdot 2 = 80; 80 - 90 = -10$ 3) $250 : (-5) = -50; -50 + 20 = -30; -30 \cdot (-3) = 90; 90 - 100 = -10$ 4) $-81 + 9 = -72; -72 : 3 = -24; -24 + 4 = -20; -20 : (-5) = 4$ **Б** 1) $-100 : 5 = -20; -20 + 18 = -2; -2 \cdot (-7) = 14; 14 - 60 = -46$ 2) $30 \cdot (-4) = -120; -120 : (-20) = 6; 6 - 36 = -30; -30 + 30 = 0$ 3) $-40 + 120 = 80; 80 : (-8) = -10; -10 - 20 = -30; -30 \cdot 3 = -90; -90 - 50 = -140$ 4) $-70 - 60 = -130; -130 : (-13) = 10; 10 \cdot 3 = 30; 30 - 50 = -20$ **В** 1) $125 \cdot (-4) = -500; -500 : (-50) = 10; 10 + 40 = 50; 50 \cdot (-3) = -150$ 2) $-23 - 25 = -48; -48 : 24 = -2; -2 \cdot (-16) = 32; 32 - 22 = 10$ 3) $-21 : 7 = -3; -3 - 17 = -20; -20 \cdot 5 = -100; -100 + 60 = -40$ 4) $75 - 100 = -25; -25 \cdot (-4) = 100; 100 + 20 = 120; 120 : (-40) = -3$ **Г** 1) $-40 \cdot 3 = -120; -120 : (-6) = 20; 20 - 60 = -40; -40 + 40 = 0$ 2) $-48 - 15 = -63; -63 : 3 = -21; -21 + 11 = -10; -10 \cdot (-6) = 60$ 3) $-350 : 70 = -5; -5 \cdot 60 = -300; -300 + 250 = -50; -50 - 25 = -75$ 4) $36 - 50 = -14; -14 \cdot 2 = -28; -28 - 14 = -42; -42 : (-3) = 14$ **Д** 1) $-94 + 24 = -70; -70 \cdot 3 = -210; -210 : (-10) = 21; 21 - 30 = -9$ 2) $100 : (-4) = -25; -25 + 13 = -12; -12 \cdot (-5) = 60; 60 - 70 = -10$ 3) $30 \cdot (-6) = -180; -180 + 80 = -100; -100 : 20 = -5; -5 - 15 = -20$ 4) $-250 - 50 = -300; -300 + 100 = -200; -200 : (-25) = 8; 8 \cdot 60 = 480$