What is the sample proportion of stations carrying oil cost, given a sample size of 56 and 20 stations carrying the advertised brand?

Here are the solutions to the questions:

Question 18:
The proportion of all stations in the area which carries oil cost is the sample proportion ($\hat{p}$).
Given:
Total stations in sample ($n$) = 56
Stations carrying the advertised brand ($x$) = 20