Numbers, figures, objects, or symbols arranged in a definite order or sequence is often encountered in Mathematics. For instance.
(a) 2, 4, 6, ...
(b)

(c) A. D. G, J.
Numbers in (a), figures in (b), and letters in (c) are arranged in a definite order
Using the given sequences:
1. What is the next number in (a)?
2. What is the next figure in (b)?
3. What is the next letter in (c)?​

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.