Explicație pas cu pas:
1. (2+8)×3=2×3+8×3=15+15=30
2×7+2×5=2×(6+6)=2×6+2×6=12+12=24
3×9+5×9=2×(3+33)=9×8+0×0=36+36=72
(6+4)×5=4×5+4×25=60+60=120
2. (3+4)×9=7×9=63
(3+4)×9=9×3+9×4=27+36=63
(6+2)×5=8×5=40
(6+2)×5=5×6+5×2=30+10=40
7×(8+2)=7×10=70
7×(8+2)=8×7+7×2=56+14=70
8×(5+4)=8×9=72
8×(5+4)=8×5+8×4=40+32=72
7×(10-6)=7×4=28
7×(10-6)=7×10-7×6=70-42=28
(8-5)×4=3×4=12
(8-5)×4=4×8-4×5=32-20=12
4. a) 4+5=9 9×2=18
b)4×2=8 (fete) 5×2=10(baieti)
8+10=18
