5X-3*5/21=5/7
5x=5/7+5/7
x=2/7
0.36*5-3/4X=3/5
3/4x=0.36*5-3/5
x=4*(0.36*5-3/5)/3
x=1.6
2/3(X+4.5)=7
x+4.5=21/2
x=6