To write a number or a relationship in the form of a ratio, you express it as a comparison between two quantities. Here are a few ways to do it: 1. Using a colon: You can write the ratio of quantity A to quantity B as A : B. Example: If you have 3 apples and 5 oranges, the ratio of apples to oranges is 3 : 5. 2. Using the word "to": You can also write the ratio as "A to B". Example: The ratio of apples to oranges is "3 to 5". 3. As a fraction: A ratio can be expressed as a fraction, with the first quantity as the numerator and the second quantity as the denominator. Example: The ratio of apples to oranges is (3)/(5). The specific form you use depends on the context of the problem.