x+21%x=36.3
x+0.21x=36.3
1.21x=36.3
x=30
x-29%x=213
x-0.29x=213
0.71x=213
x=300
60%x+25%x=10.2
0.6x+0.25x=10.2
0.85x=10.2
x=12
90%x-18%x=54
0.9x-0.18x=54
0.72x=54
x=75