Đáp án:
↓↓
Giải thích các bước giải:
`1)`
`a)`
`( x - 4 + 6 ) × 7 - 5 = 65`
`( x - 4 + 6 ) × 7 = 65 + 5 `
`( x - 4 + 6 ) × 7 = 70`
`x - 4 + 6 = 70: 7`
`x - 4 + 6 = 10`
`x - 4 = 10 - 6`
`x - 4 = 4`
`x = 4 + 4`
`x = 8`
`b)`
`x : 4/5 = 25/8 : 4/15`
`x : 4/5 = 375/32`
`x = 375/32 × 4/5`
`x = 75/8`
`2)`
`a)`
`( 100 + 67 ) × 67 + ( 200 - 33 ) × 33`
`= 167 × 67 + 167 × 33`
`= 167 ×( 67 + 33 )`
`= 167 × 100`
`= 16700`
`b)`
`112,37 × 4,29 - 4,29 × 12,37 × 50 × 12,37`
`= 4,29 × ( 112,37 - 12,37 + 50 )`
`= 4,29 × 150`
`= 643,5`
`c)`
`124 × 76 + 12 × 248`
`= 124 × 76 + 24 × 124`
`= 124 × ( 76 + 24 )`
`= 124 × 100`
`= 12400.`