đề yêu cầu gì ạ?

`3/8 +4/10`

`=3/8 +2/5`

`=15/40 + 16/40`

`=(15+16)/40`

`=31/40`

`3/8 +4/10`

`=3/8 +2/5`

`=15/40 + 6/40`

`=(15+6)/40`

`=21/40`

`3/7 +4/10`

`= 30/70 + 28/70`

`=(30+28)/70`

`=58/70=29/35`

`3/7 +4/10`

`= 30/70 + 28/70`

`=(30+28)/70`

`=58/70`

`24-2/5-5/12`

`= 1440/60 - 24/60 - 25/60`

`= (1440-24-25)/60`

`=1391/60`

b)

`15-3(3x+18)=36`

`=> 3(3x+18)=15-36`

`=> 3(3x+18)=-21`

`=> 3x+18=-21:3`

`=> 3x+18=-7`

`=> 3x=-7-18`

`=> 3x=-25`

`=> x=-25:3`

`=> x=-25/3`

c)

`-12+(3-x)=25`

`=>-12+3-x=25`

`=>-x=25+12-3`

`=>-x=34`

`=>x=-34`

d)

`100-90xx(x:2-1)=-10`

`=>90xx(x:2-1)=100-(-10)`

`=>90xx(x:2-1)=110`

`=>x:2-1=110:90`

`=>x:2-1=11/9`

`=>x:2=11/9 +1`

`=> x:2=20/9`

`=> x=20/9 xx2`

`=> x=40/9`

`1/4=(1xx5)/(4xx5)=5/20`

`2/5=(2xx4)/(5xx4)=8/20`