Like many ratio problems, you would want to express this relationship as a unit rate. This means you want to display the findings as the amount of something per another quantity. In this instance, you want to find out a miles per hour unit rate. You could approach this as setting up equivalent fractions, where the numerator represents miles travelled and the denominator represents hours. In the first fraction, it would be represented as 180/4 (180 miles and 4 hours) and this would be set to X/1, because we want to find the unit rate (1 hour) and we need to know how many miles are travelled. At this point, we could cross multiply and divide (180 * 1, then divided by 4). The answer would be 45 miles can be travelled in one hour. There are other ways to solve this problem, but in terms of determining unit rate, this method works well when the numbers are not so easily to manipulate as these numbers were.