(100 X)/(64-X)=3
100X=3(64-X)
100X=192-3X
100X+3X=192
103X=192
X=192/103
(100 -X)/(64-X)=3
100-x=3(64-x)
100-x=192-3x
-x+3x=192-100
2x=92
x=46