3/4x=(510-x)*2/3
3/4x=340-2/3x
3/4x+2/3x=340
9/12x+8/12x=340
17/12x=340
x=340x12/17
x=240
(90-1/2*400-x)*1/3=1/4x
(90-200-x)=3/4x
3/4x+x=90-200
7/4x=-110
x=-110x4/7
x=-440/7
3/5x=(18-x)*1/2+2
0.6x=9-0.5x+2
0.6x+0.5x=9+2
1.1x=11
x=10