x-30%x=2.4
0.7x=2.4
x=24/7
2/3x+1/4=12.6
2/3x=12.6-0.25
2/3x=12.35
x=18.525
1/5x-0.8=0.3
1/5x=0.3+0.8
1/5x=1.1
x=5.5