Each month for 9 months jordan buys 2 sports books .how many more sports books does he need to buy before he has 25 sports books

Step 1:
Multiply months by books per month
9 months * 2 books/most= 18

Step 2:
Subtract answer to step 1 from the total books wanted (25).
25-18= 7 more books needed

Hope this helps! :)

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.