Answer: 9 cm
Step-by-step explanation: Let's create a proportion. 20/50 = x/22.5. Using cross-multiplying, we get 22.5 x 20 = 50 times x. We can simplify this equation to get 450 = 50x. To get x by itself, we divide both sides of the equation by 50, leaving us with 9 = x, or 9 cm