Angles Equations

How would you SET UP the equation to solve for x?

• x - 5 = x + 11

• x - 5 + x + 11 = 180

Answer explanation

These are supplementary angles. They are not equal. They add up to 180.

x - 5 + x + 11 = 180

Combine like terms! What do you get?

• 2x + 6 = 180

• 2x + 16 = 180

2x + 6 = 180

What do you do next?

• Divide by 2 on both sides

• Subtract 6 on both sides

• Add 6 on both sides

• Multiply by 2 on both sides

2x + 6 = 180

Subtract 6 on both sides.

Then, divide by 2 on both sides. What does x = ?

• x = 172

• x = 174

• x = 90

• x = 87

How would you SET UP your equation?

• 9x + 7 = 10x - 2

• 9x + 7 + 10x - 2 = 180

Answer explanation

These are vertical angles. They are congruent, so they are equal to each other. So when you set up the equation, you make set them equal to each other.

9x + 7 = 10x - 2

Next step: Subtract 9x on both sides. What do you get?

• 7 = x - 2

• 7 = 19x - 2

• 7 = 10x - 2

• 7 = 9x - 2

7 = x - 2

What does x = ?

• x = 7

• x = 5

• x = 9

• x = 14

How would you SET UP your equation?

• 4x + 13 = 6x - 3

• 4x + 13 + 6x - 3 = 180

4x + 13 = 6x - 3

Subtract 4x on both sides. What do you get?

• 13 = 10x - 3

• 13 = 6x - 3

• 13 = x - 3

• 13 = 2x - 3

13 = 2x - 3

What does x=?

• x = 10

• x = 8

• x = 16

• x = 5