Kevin sticks his hand into the M & M jar and removes one M & M and places
it on his desk. The amount of bacteria on the M&M is modeled by the
equation below for t hours. Based on the equation, approximately how
many bacteria would be on the M & Mafter 15 hours?"

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.