Exercise 26 Page 395

We want to find the value of $x$ in the given triangle.

To do so, we will first recall a key piece of information!

Exterior Angles of a Triangle
The measure of an exterior angle of a triangle is equal to the sum of the measures of its two remote interior angles.

With this rule, we can write an equation in terms of

x .

x^{\circ} = 100^{\circ} + 25^{\circ}

Now, we can solve this equation for

x .

For simplicity, we will not include the degree symbol.

x = 100 + 25

Add terms

x = 125