6.75-2又2/9+3又1/4-3又9/7
=(6又3/4+3又1/4) -(2又2/9+3又7/9)
=10-6
=4

2又1/3-3/5×1.25
=7/3-3/5×5/4
=7/3-3/4
=19/12

1又8/15÷[3-（3/4+1/3）]
=23/15÷[3-（9/12+4/12）]
=23/15÷[3-13/12]
=23/15÷23/12
=23/15×12/23
=12/15
=3/5

3/8x=26-3/4x
3/8x+3/4x =26
9/8x=26
x=26×8/9
x=208/9

4[x+1]=6x
4x+4=6x
4=6x-4x
4=2x
2=x
x=2

5[2x-1.2]=4
5[2x-6/5]=4
10x-6=4
10x=4+6
10x=10
x=1
希望對(duì)你有幫助哦