b. 720 : ( a ×3 + a × 5) = 2 × 3
Giải thích
b. 720 : ( a ×3 + a × 5) = 2 × 3720 : [a ×( 3 + 5)] = 6720 : ( a × 8) = 6a × 8 = 720 : 6a × 8 = 120a = 120 : 8a = 15
b. 720 : ( a ×3 + a × 5) = 2 × 3720 : [a ×( 3 + 5)] = 6720 : ( a × 8) = 6a × 8 = 720 : 6a × 8 = 120a = 120 : 8a = 15