Solving Equations: Word Problems - Examples & Practice

In the morning, Esther biked from home to school at an average speed of $x$ miles per hour. In the afternoon, having lent her bike to a friend, Esther walked back home along the same route at an average speed of $3$ miles per hour. Her average speed for the round trip was $5$ miles per hour. What is the value of $x$?

Source: Math Prize for Girls