Using sohcahtoa; you have an angle and the hypotenuse. The side you are trying to find is adjacent to the angle therefore you use cos.
Cos(angle)=adjacent side/hypotenuse
Plug in to get cos(20)=y/8
Solve for y to get
Y=8*cos(20)
Solve for y
Y=7.51
Round to the nearest tenth 
Y=7.5