since we already know he bought 3 more than her we can subtract 3 from 15 which is 12, since he bought twice more than her we can divide 12 by 3 which is 4. Multiply by 2 and you get 8, and when you add it to the subtracted 3 you get 11. So she bought 4 and he bought 11
we have x+4 and 3 times the fraction with x+4 in denomenator with the fraction 3/3 times the fraction with 3 in denomenator with the fraction x+4 we get since common denoms, can add them to get that is simplified
