A ratio compares two quantities. Ratios show how much of one thing there is relative to another. For example, if a recipe uses 2 cups of flour and 3 cups of sugar, the ratio of flour to sugar is 2 : 3.
To simplify, divide both numbers by their greatest common divisor (GCD). For example, 12 : 16 becomes 3 : 4 after dividing both by 4.
If two ratios are equal, you can cross-multiply. For 2 : 3 = 4 : X, multiply the inner terms (3 × 4 = 12) and divide by the outer term 2, so X = 6.