Câu `1:`
`(3/8 + (-3)/4 + 7/12) : 5/6 + 1/2`
`= (3/8 - 3/4 + 7/12) . 6/5 + 1/2`
`= (3/8 - 6/8 + 7/12) . 6/5+ 1/2`
`= ((-3)/8 + 7/12) . 6/5 + 1/2`
`= ((-18)/48 + 28/48) . 6/5 + 1/2`
`= 5/24 . 6/5 + 1/2`
`= 1/4 + 2/4`
`= 3/4`
Câu `2:`
`2/(3.5) + 2/(5.7) + 2/(7.9) + ... + 2/(99.101)`
`= 1/3 - 1/5 + 1/5 - 1/7 + ... + 1/99 - 1/101`
`= 1/3 - 1/101`
`= 98/303`