`1/7+(-9/27)+10/7+(-4/7)`
`= (1/7 + (-4)/7+10/7) +(-9/27)`
`= 7/7 +(-9/27)`
`= 1 +(-9/27)`
`= 27/27 + (-9/27)`
`=18/27`
`=2/3`
__
`1,3 xx2 1/4 -1,3 xx3 1/4`
`= 1,3 xx 9/4 -1,3 xx 13/4`
`=1,3 xx (9/4-13/4)`
`=1,3xx(-4)/4`
`=1,3 xx (-1)`
`=-1,3`
__
`1/4: x = 2,4 -4/5`
`=> 1/4 : x= 12/5 -4/5`
`=> 1/4 : x=8/5`
`=> x=1/4 : 8/5`
`=> x= 1/4 xx 5/8`
`=> x= 5/32`
__
`5/4 ( x- 3/5)= -1/8`
`=> x-3/5 = -1/8 : 5/4`
`=> x-3/5 = -1/8 xx 4/5`
`=> x-3/5 =-4/40`
`=> x-3/5 =-1/10`
`=> x=-1/10 +3/5`
`=> x=-1/10 + 6/10`
`=> x= 5/10`
`=>x=1/2`
` @ yngoc`