Răspuns:
18)
(45:5+45:9):7+2×10:10
(9+5):7+2×10:10
=14:7+2×10:10
=2+2×10:10
=2+20÷10
=2+10
=12
19)
2×3×5+60:10:6-31
=6×5+60:10:6-31
=30+60:10:6-31
=30+6:6-31
=30+1-31
=31-31=0
20)
(100-60-30)×5+(10-6:3):8
=(40-30)×5+(10-2):8
=10×5+8:8
=50+1
=51
21)
45:5+54:6-(54+45):(4+5)
=45:5+54:6-99:9
=9+9-11
=18-11
=7
22)
(9×7-6:3)-(81-8×8)
=(63-3)-(81-64)
=61-17
=44
23)
(8×5:10+6×6)-(10+3×3)
=(40:10+36)-(10+3×3)
=(4+36)-(10+9)
=40-19
=21
