Đáp án + Giải thích các bước giải:
`a) x/4 + 1/4 = 25/28` $\\$ `=> (x + 1)/4=25/28` $\\$ `=> [7(x +1)]/28=25/28` $\\$ `=> 7(x + 1) = 25 => x + 1 = 25/7` $\\$ `=> x = 25/7 - 1 = 18/7`
`b) 2/5 + 3/x = (-1)/35` $\\$ `=> 3/x = (-1)/35 - 2/5` $\\$ `=> 3/x = (-1)/35 - 14/35` $\\$ `=> 3/x = (-15)/35 = (-3)/7 = 3/(-7)` $\\$ `=> x= -7`
`c) 1/5 + x - 7/3 = 1/2` $\\$ `=> 1/5+x=1/2+7/3` $\\$ `=> 1/5+x=17/6` $\\$ `=> x = 17/6 - 1/5 = 79/30`
`d) (-1)/3-x-4/5=4/15` $\\$ `=>(-1)/3 - x=4/15 + 4/5` $\\$ `=> (-1)/3 - x = 4/15 + 12/15 = 16/15` $\\$ `=> x = (-1)/3 - 16/15 = (-7)/5`