In a previous article, we looked at how simple algebraic problems can be solved, the case in point being a rectangle. In this example, notice how similar steps have been followed, except that instead of a perimeter of a rectangle, we shall be considering the angles in a triangle.

As before, the material has been provided by BBC Bitesize Find the size of angle .

### 1. What Do I Have To Do?

Read the question through twice. Highlight or underline the important pieces of information in the question, as done above.

### 2. What Information Do I Need?

The question is asking for the size of angle . The question involves work on geometry and it may be necessary to use some angle facts.

In this diagram there is a triangle and a straight line. Although the angle looks obtuse, it might not be. Write any angles onto the diagram.

### 3. What Information Don’t I Need?

Everything in this question is relevant to working out the answer.

### 4. What Maths Can I Do?

Step A

Use the fact that the sum of the angles in a triangle are equal to 180° to create an equation. Step B

Simplify the equation: Step C

Solve the equation to find the value of . Subtract 37 from both sides: Divide both sides by 11: Step D

Use the answer to step C to work out the value of each angle.  , so substitute 13 into the expression . Therefore the value of the highlighted angle is 23°.

Step E

Use the fact that angles on a straight line add up to 180° to work out the value of . Therefore the value of is 157°.

### 5. Is my solution correct?

It is important to check any calculations at the end.

Go through and check them carefully.

Work out the other angles in the triangle:  Add these two angles to 23° and it should equal 180°. ### 6. Have I completed everything?

The answer should be the size of an angle.

Make sure the answer has the unit (degrees) on it.