Dorothy is 6 years older than Ricardo The product of their present ages is twice what the product of their ages was 6 years ago How old is Dorothy?

Answer 1

d = r + 6

now you make the equation relating what happened 6 yrs ago, remembering that then they were r-6 and d-6:

dr = 2(r-6)(d-6)

plug the first eqn into the second one and solve:

r(r+6) = 2(r-6)(r)

you can cancel an r, since r isn't 0!

r+6 = 2(r-6)

r=18

So Ricardo is 18 and his sis is 24.