Đáp án `+` Giải thích các bước giải`:`

`a) (2,5xx1,2+x-2,5):2,5=4`

`3+x-2,5=4*2,5`

`3+x-2,5=10`

`3+x=10+2,5`

`3+x=12,5`

`x=12,5-3`

`x=9,5`

Vậy `x=9,5`

`b) 387xx0,25-(x:4+x:0,125):0,5=14,25`

`96,75-(x xx 0,25+x xx 8)xx2=14,25`

`96,75-[x xx (0,25+8)]xx2=14,25`

`96,75-x xx 8,25xx2=14,25`

`x xx 16,5=96,75-14,25`

`x xx 16,5=82,5`

`x = 82,5:16,5`

`x= 5`

Vậy `x=5`

`c) x:2,5-68,76=72,54`

`x:2,5=72,54+68,76`

`x:2,5=141,3`

`x=141,3xx2,5`

`x=353,25`

Vậy `x=353,25`

`d, 72,64-x xx 2,5=44,4`

`x xx 2,5=72,64-44,4`

`x xx 2,5=28,24`

`x=28,24:2,5`

`x=11,296`

Vậy `x=11,296`

`e, x xx 4+20/100xx x =8`

`x xx 4+0,2xx x=8`

`x xx (4+0,2)=8`

`x xx 4,2=8`

`x=8:4,2`

`x=40/21`

Vậy `x=40/21`

`g) 72,64-x xx 2,5=68,76`

`x xx 2,5=72,64-68,76`

`x xx 2,5=3,88`

`x=3,88:2,5`

`x=1,552`

Vậy `x=1,552`