Đáp án:
Giải thích các bước giải:
`1. y × 3 + y × 8 - y × 6 + 10 × y + 720 = 1260`
`y × 3 + y × 8 - y × 6 + 10 × y - 1260 - 720`
`y × (3 + 8 - 6 + 10) = 540`
`y × 15 = 540`
`y = 540 : 15`
`y = 36`
`2. 12 × (2 × y - 4) + (7 - 3 × y) × 5 + 6 × (8 + 10 × y) = 35708`
`24 × y - 48 + 35 - 15 × y + 48 + 60 × y = 35708`
`24 × y - 15 × y + 60 × y = 35708 + 48 - 35 - 48
`y × (24 - 15 + 60) = 35673`
`y × 69 = 35673`
`y = 35673 : 69`
`y = 517`
`3. 8 × (y + 3) + 6 × (8 - y) + (5 × y - 2) × 7 = 3684`
`8 × y + 24 + 48 - 6 × y + 35 × y - 14 = 3684`
`8 × y - 6 × y + 35 × y = 3684 - 24 - 48 + 14 `
`y × (8 - 6 + 35) = 3626`
`y × 37 = 3626`
`y = 3626 : 37`
`y = 98`
`4. 8 × (2 × y + 9) + (12 - y) × 3 + 4 × (2 × y - 3 - 6 × y) = 18`
`16 × y + 72 + 36 - 3 × y + 8 × y - 12 - 24 × y = 18`
`16 × y - 3 × y + 8 × y - 24 × y = 18 - 72 - 36 + 12`
`y × (16 - 3 + 8 - 24) = 18 - 72 - 36 + 12`
`y × (-3) = -78`
`y = -78 : (-3)`
`y = 26`
(Lớp `5` chưa học số âm mà nhỉ?)
`5. 2 × (4 × y - 8) - 6 × (y + 3) = 35712`
`8 × y - 16 - 6 × y + 18 = 35712`
`8 × y - 6 × y = 35712 + 16 - 18`
`(8 - 6) × y = 35710`
`2 × y = 35710`
`y = 35710 : 2`
`y = 17855`
