1)2/5*2/5=4/25
2)4 1/3-4/25=4 25/75-12/75=4 13/75
3)4 13/75+3 1/75=7 14/75
4)7 14/75:4/75=539/75*75/4=539/4=134 3/4=134,75
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(3 1/2+4/9)x+3/18=5/18
3 17/18x+3/18=5/18
3 17/18x=5/18-3/18
3 17/18x=2/18
x=2/18:3 17/18
x=2/18*18/71
x=2/71