You could first solve for y, assuming x is 0, and y = 6. Then solve for x, and that means y = 4.
Your answer would be 4379 members because at the very beginning you had started off with 4372 members, however as the months go by changes happen. On october, it changed by -10, meaning that 10 students left the school meaning 4372-10=4362 members remaining. Then there's november with -8, so you subtract 8 from your new total 4362-8=4354. Then december comes, and this time it's a positive number, so you have to add 23 to 4354, giving you a new total of 4377. Then there's january, and its back to a negative number so you subtract 12 from 4377, 4377-12=4365. Then february comes and it's a change of a positive number, so you add 3 to the 4365, giving you 4368. And then finally by march, it's another positive number so you add 11 to your total, giving you 4379 students which are now at school. So basically if it's a negative change, subtract from the total, and if it is a positive, add to it. And you have to continue with the total that you got from the previous change that you did. Hope this was helpful
A + b = 15 ..... eq 1
a – b = 12 ...... eq 2
So a = 15 – b
Substitute in eq 2 :
15 – b – b = 12
15 – 2b = 12
–2b = 12 – 15
b = 1.5
So a = 15 – 3/2 = 13.5
4ab = 4 x 13.5 x 1.5 = 81
