How do we find x to get the answer?

That line that is made out of angles 1 and 2 is straight. What we know about straight lines is that they're 180°. This means that ∠1 and ∠2 are supplementary, adding up to 180°.

∠1 + ∠2 = 180
∠1 = (x + 81)
∠2 = (2x)

(x + 81) + 2x = 180
3x + 81 = 180
3x = 99
x = 33

The answer is x = 33.

All lines equal up to 180 degrees. In order to get the straight line, we need to add degree 1 and degree 2.

(x+81)+(2x)=180
Now add the x's.

3x+81=180
3x=99
x=33