### Home > CC3 > Chapter Ch6 > Lesson 6.1.3 > Problem6-30

6-30.

Solve the problem below by defining a variable and then writing and solving an equation.

The perimeter of a triangle is $31$ cm. Sides $\#1$ and $\#2$ have equal length, while Side $\#3$ is one centimeter shorter than twice the length of Side $\#1$. How long is each side?

Refer to the Math Notes box in Lesson 1.1.3 to review the 5-D Process.

$\text{Side #}1=\ \text{Side #}2$
$\text{Side #}3=2\left(\text{Side #}1\right)-1$
Make sure the sides sum to $31$.

$\text{Side #}1=\text{Side #}2\ \text{cm}$
What is the length of Side $\#3$?