1. Tính
`a) 5^7 : 5^4 - ( 3^2 - 2^3 )`
`= 5^3 - (9 - 8) `
`= 125 - 1`
`= 124`
`b) (-7/5) + 8/13 + (-3/5) + 5/13 `
`= [(-7/5) + (-3/5)] + (8/13 + 5/13)`
`= (-10/5) + 13/13`
`= -2 + 1`
`= -1`
2. Tìm x
`( x - 1/4 ) : 4/5 = 15/16`
`=> x - 1/4 = 15/16 × 4/5`
`=> x - 1/4 = 3/4`
`=> x = 3/4 + 1/4`
`=> x = 1`
(Chúc bạn học tốt)