a) (-5)x50+20x[20-(8-5)] =
-250+20·(20-3) =
-250+20·17 =
-250+340 =
90
b) [72:(-3)]:(14-6) =
-24÷8 =
-3
c) (17-2):3-4+(-2) =
15÷3-4-2 =
5-4-2 =
-1
d)(-5)[30-(7-3)] =
(-5)(30-4) =
-5·26 =
-130
e) 23(81-78)-7(33-26) =
23·3-7·7 =
69-49 =
20
f) 3(4-1)-4(3-4)+5(7-5) =
3·3-4·(-1)+5·2 =
9+4+10 =
23
