C expression, we can use the sum function in python. For e, the command.
sum(x**2 for x in range (1,101))
e sum of the squares of the first hundred natural numbers.
1) Find the sum of the first 25 terms of each of the arithmetic sequenc
below.
1) 11, 22, 33, ii) 12, 23, 34, iii) 21, 32, 43,
iv) 19, 28, 37, .. v) 1, 6, 11,​

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.