PSAT 8/9 Math Practice Test

The main idea is to model each person’s age in terms of d and then add them together. Dave is d years old. Sonya is three times Dave’s age, so Sonya’s age is 3d. Gavin is a fixed 20 years old. Add them: d + 3d + 20 = 4d + 20. This expression gives the total of their ages in terms of d. The other options miss either Gavin’s 20, or combine terms incorrectly, or give a specific number instead of an expression in d.