I'm having trouble setting up these kind of math questions: Sally is 4/5 as old as her sister Jane. Their brother Dick's age is 1/3 more than Jane's. If Dick is 20, how old is Sally? Know here is the explanation from kaplan.... This is a relatively easy problem. You just have to be careful when you set up your equations. Let's let S be Sally's age, in years, J be Jane's age, in years, and D be Dick's age, in years. We know that Sally is 4 5 as old as Jane, thus S = 4/5 J . We know that Dick's age is1/3 more than Jane's age, thus Dick's age is 4/3 times Jane's age or D = 4/3j J . We are given that Dick's age is 20. We have 20 = 4/3 J . To get J, we multiply both sides of this equation by3/4 , so J = 3/4 D = 3 4 (20) = 3 × 5 = 15, therefore Jane is 15 years old. Now we want to find Sally's age. We know that S = 4 5 J meaning that Sally's age is 4 5 of Jane's age. We know that Jane's age is 15, therefore Sally's age is 4 5 of 15, or 12. Sally's age is 12 and that is answer choice C. The part im stuck at is when they say We know that Dick's age is1/3 more than Jane's age, thus Dick's age is 4/3 times Jane's age or D = 4/3j How do you get D= 1/3 + J (i don't know if this set up is even right) to D=4/3J?