Câu 1
`1/2`+`1/3`+`1/4`
=`6/12`+`4/12`+`3/12`
=`13/12`
b)(27,09+0,91)x25,4
=28x25,4
=711,2
c)`13/17`+`1/11`+`4/17`+`5/11`+`10/22`
=(`13/17`+`4/17`)+(`1/11`+`5/11`+`5/11`)
=`1+1`
=`2`
`d)77x43-43+24x43`
`=43x(77+24-1)`
`=43x100`
`=4300`
Câu 2
`a)34,8-y=10,5`
`y=34,8-10,5`
`y=24,3`
`b)52x(y:78)=3380`
`y:78=3380:52`
`y:78=65`
`y=65x78`
`y=5070`