Question

Find the value of x in the equation

Answer 1

Answer: 10.5 (equivalent to the fraction 21/2)

To get this answer, you set 10x-15 equal to 90 and solve for x. The reason why these two angles are equal is because they are vertical angles.

10x-15 = 90

10x-15+15 = 90+15 ...... add 15 to both sides

10x = 105

10x/10 = 105/10 ...... divide both sides by 10

x = 105/10

x = 21/2 is the answer in fraction form

x = 10.5 is the answer in decimal form

Answer 2

You'll use what the vertical angles theorem tells you to solve this.

The vertical angles theorem says that vertical angles are congruent, which is what the angle with (10x-15) and the opposite angle (90) are.

Since they are vertical angles, they are congruent so you can set up an equation where they are equal and solve for x.

(10x-15) = 90

1. Get rid of the parentheses.

10x-15 = 90

2. Add 15 to both sides.

10x = 105

3. Divide both sides by 10.

x = 10.5

Answer is:

x = 10.5