If we know that 455 students are in school today and that number represents 70% attendance, we can write an equation to figure out how many students go to the school.

The number of students in school today is known in two different ways: as 70% of the students in the school, and also as 455. If $s$ represents the total number of students who go to the school, then 70% of $s$, or $\frac{70}{100}s$, represents the number of students that are in school today, which is 455.

We can write and solve the equation: $$\begin {align} \frac{70}{100}s&=455\\ s&=455\div\frac{70}{100}\\ s&=455\boldcdot \frac{100}{70}\\ s&=650\end{align} $$

There are 650 students in the school.

In general, equations can help us solve problems in which one amount is a percentage of another amount.