Many problems can be solved by writing and solving an equation. Here is an example:

Clare ran 4 miles on Monday. Then for the next 6 days, she ran the same distance each day. Clare ran a total of 22 miles during the week. How many miles did she run on each of the 6 days?

One way to solve the problem is to represent the situation with an equation, $4+6x = 22$, where $x$ represents the distance, in miles, Clare ran on each of the 6 days. Solving the equation gives the solution to this problem.

$\begin{aligned} 4+6x &= 22 \\ 6x &= 18 \\ x &= 3 \\ \end{aligned}$

Clare ran 3 miles each day.