The Least Common Multiple of 10 and 6 is 2 so you divide 10 by 2, which is 5, and divide 6 by 2, which is 3. you subtract 3 from 5 which is 2. this means that in order to get 3 for x you got to divide 15 by 5 which is 3. This means you multiply 5 by 5 which is 25.
