Question

5. In the figure below, what is the value of angle x?

Answer 1

x = 30

Explanation:

Vertical angles (angles that form when 2 lines forms a cross) are equal.

The vertical angle (top left of 3x + 10 angle) of the "3x + 10" angle is the angle ADJACENT to 80 degree angle.

When we have 2 adjacent angles like this, their sum is equal to 180, so that angle would be:

180 - 80 = 100

Now, this 100 degree angle is a vertical angle to "3x+10" angle. So they are EQUAL. We can write an equation and solve for x now:

`3x+10=100\\3x=100-10\\3x=90\\x=(90)/(3)\\x=30`

Hence, x = 30