4^2*y^2-0,5^2=(2у-0,5)(2у+0,5)
1.1)x+x-2=18
2x=20
x=10
2)2x+2=18
2x=16
x=8
3)3x=18
x=6
4)x+1/2x=18
3/2x=18
x=12