x/5+1/4=x/4-1/5
x/4-x/5=1/4+1/5
5x-4x=5+4
x=9
10-2x=8+2x
2x+2x=10-8
4x=2
x=1/2
2/3+3/4=3/4+2x/3
2/3+3/4-3/4=2x/3
2/3=2x/3
2x=2
x=1