Question

For what value of x is line a parallel to line b?

x=?

URGENT THANKSSSS

Answer 1

The angle of 80 degrees is the same angle as the one with the equation. That equation has to equal 80 somehow.
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80 - 20 (from equation) = 60
60 ÷ 2 (also from equation) = 30
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x = 30 To make sure plug it in
(2 x 30)+ 20
60 + 20 = 80
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x should equal 30

Please correct me if wrong

Answer 2

`x=30`

Explanation:

According to Corresponding Angles Theorem, given one pair of parallel lines cut by another transversal one, the pair of corresponding angles have the same measure.

Therefore:

`2x+20=80\\2x=60\Rightarrow x=30`

Geometrically proving:

Since the angle
`(2x+20)` is 80º then we can state its Alternate Interior angle (in blue) values also 80º. In addition to this, the Vertex Angle Theorem confirms that.

Algebraically, just plug in 30º for x, then solve it to prove it:

`2(30)+20=80\Rightarrow 80=80`