`a)``2/3.x+1/5=7/10-x`
` 2/3.x + x= 7/10 - 1/5`
` 2/3.x + x= 7/10 - 2/10`
` 5/3.x = 5/10 = 1/2`
` x = 1/2 : 5/3`
` x = 1/2 . 3/5`
` x = 3/10`
`b)``3` `1/5x+16``3/4=-13,25`
`16/5x + 67/4 = (-1325)/100`
`16/5x = (-1325)/100 - 67/4`
`16/5x = 5300/400 - 6700/400`
`16/5x = (-1400)/400 = (-7)/2`
` x = (-7)/2 : 16/5`
` x = (-7)/2 . 5/16`
` x = (-35)/32`
Câu `c )` làm sau