Đáp án:
Giải thích các bước giải:
`A=3/13+2/5+8/13+8/15=(3/13+8/13)+(2/5+8/15)`$\\$ `=11/13+(6/15+8/15) =11/13+14/15 = 347/195`$\\$ `B=3/5xx5/7+17/10xx5/7 =5/7xx(3/5+17/10) `$\\$ `=5/7xx(6/10+17/10) =5/7xx23/10 =23/14`$\\$ `C=5/9xx12/13+12/13xx5/18+1/6xx12/13 =12/13xx(5/9+5/18+1/6)`$\\$ `=12/13xx(10/18+5/18+3/18) =12/13xx1 =12/13`$\\$ `D=6/7xx8/8-8/9xx5/14 =6/7-20/63 =34/63`$\\$