Математика 3 класс помогите пожалуйста

1)40*2=80 2)42*3=129 3)45*10=450 4)36*2=72 5)54*3=162 6)24*3=72 7)21*4=84

(408-400) × 5 = 8 × 5 = 40. (126 - 120) × 7 = 6 × 7 = 42. 9 × (345 - 340) = 9 × 5 = 45. 4 × (709 - 700) = 4 × 9 = 36. 6 × (289 - 280) = 6 × 9 = 54. (233 - 230) × 8 = 3 × 8 =24. 3 ×(807 - 800) = 3× 7 = 21. (42 - 35) × 3 = 7 × 3 = 21. 7× (601 - 600) = 7 × 1 = 7. 10 × (212 - 212) = 10 × 0 = 0. (907 - 900) × 7 = 7 × 7 = 49. (548 - 540) × 8 = 8 × 8 = 64. 5 × (240 - 230) = 5 × 10 = 50