1 a) (13+2×12+337-120)×20+1=
(13+24+337-120)×20+1=
(37+337-120)×20+1=
(374-120)×20+1=
252×20+1=
5040+1=5041
b) 12×15=180
12+15=27
180-27=153
c) ab+ab0+ab00-ab×11=3500
35+35×10+35×100-35×11=3500
35+350+3500-385=3500
385+3500-385=3500
3885-385=3500
3500=3500
2 a) 94×85×9+94×85-94×750=
7.990×9+7.990-70.500=
71.910+7.990-70.500=
79.900-70.500=9 400
b) 3116×12+3116×7-3116×9=
37.392+21.812+28.044=
59.204+28.044=87.248
