Using SOH (Sin=Opposite/Hypotenuse)
Opposite of 20 degrees is the side labeled x. 8 is the hypotenuse.
Sin(20)=x/8
Put Sin(20) into a calculator. (You should get 0.3420)
Start with 0.3420 = x/8
Then swap sides x/8 = 0.3420
Multiply both sides by 8
x = 0.3420 x 8
x = 2.736
Your answer would be sin20 times 8