Question

Find the value of x that makes a || b

Answer 1

x = 15°

Explanation:

Notice that if A is // to B, then ∠2 and ∠4 are supplementary angles, i.e they add up to 180°. We can write this as:

∠2 + ∠4 = 180

(2x + 10) + (4x + 80) = 180

2x + 10 + 4x + 80 = 180

6x + 90 = 180

6x = 180 - 90

6x = 90

x = 15°

Answer 2

15

Explanation:

So angle 2 and angle 4 have a relationship that is called same-side interior or consecutive interior angles. The name there depends what class you are in but they mean the same thing.

If you have the transversal goes through parallel lines, then same-side interior angles will add up to 180 degrees.

So you are trying to solve the following equation for x:

angle2+angle4=180

2x+10+4x+80=180

Combine like terms:

6x+90=180

Subtract 90 on both sides:

6x =90

Divide both sides by 6:

x =90/6

Simplify:

x =15

15 is x so that the lines are parallel