Đáp án:
`A=1/2.3+2/3.5+3/5.8+4/8.12+5/12.17+6/17.23+7/23.30=7/15`
Giải thích các bước giải:
`A=1/2.3+2/3.5+3/5.8+4/8.12+5/12.17+6/17.23+7/23.30`
`A=1/2-1/3+1/3-1/5+1/5-1/8+1/8-1/12+1/12-1/17+1/17-1/23+1/23-1/30`
`A=1/2-1/30`
`A=15/30-1/30`
`A=14/30`
`A=7/15`
Vậy `A=7/15`