What is the value of X?

The answer is option C.

So better not to try and get the value of X by substituting values. Rather try to check whether they are solvable or not.

A. 8X+16Y+24K = 80

B. 18X+24Y+36K= 180

Let me write equation A in the form:- lX + mY + nZ = 80
and equation B in the form:- pX + qY + rZ = 180

So to check whether we can solve this find the value of l:m:n and p:q:r and compare both of them. (we are find the ratio of coef. here)

For equation A, we have l:m:n = 8:16:24 which is equal to 1:2:3
For equation B, we have p:q:r = 18:24:36 which is qual to 3:4:6

We can see here that the ratio of second and the third terms in this ratio are equal (which is 1:2) but the ratio of the first term is not equal with respect to any other term. So somehow if you subtitute, the value of X (the first term) can be found out and not the remaining terms.