Đáp án:
$\\$
`a,`
`1/3 + 8/15 - 7/5`
`= 5/15 + 8/15 - 21/15`
`= (5 + 8 - 21)/15`
`= (-8)/15`
$\\$
`b,`
`(-11)/23 × 2/5 + (-2)/5 × 12/23`
`= (-11)/23 × 2/5 + 2/5 × (-12)/23`
`= 2/5 × ( (-11)/23 +(-12)/23)`
`= 2/5 × (-1)`
`= (-2)/5`
$\\$
`c,`
`2/15 -1,6÷(75%+ 5 1/4)`
`= 2/15 - 8/5 ÷ (3/4 + 21/4)`
`= 2/15 - 8/5 ÷ 6`
`= 2/15 - 8/5 × 1/6`
`= 2/15 - 4/15`
`= (-2)/15`
