Answer :
It is given that 20 runners were faster than Colby and that they were 25% of the runners.
It is required to find the total number of runners in the race.
Let the total number of runners be x.
Since 25% of the runners are 20 in number, it follows that:
[tex]\begin{gathered} 25\%\times x=20 \\ \Rightarrow\frac{25}{100}x=20 \\ \Rightarrow\frac{1}{4}x=20 \\ \text{ Multiply both sides by }4: \\ \Rightarrow4\times\frac{1}{4}x=4\times20 \\ \Rightarrow x=80 \end{gathered}[/tex]The total number of runners in the race is 80.