It would be nice if someone can help me. i’m failing school and i really need help. thank you:).

only C is non-linear

Step-by-step explanation:

A linear equation is of the form;

y = mx + c

we have single powers of x and y; also, there is no product of x and y

Thus, we have;

a; 12x + 3y = 7

y =( -12x + 7)/3

this shows we have a linear equation

b. y + x = 4x + 5

y = 4x-x + 5

y = 3x + 5

This is a linear equation

c. y = 8/x^2

This is non-linear; we already have one power of x as 2

Khalid and Sue's Height together is 126 Inches. The difference is 6 inches, so therefore you subtract 6 from the total getting you 120 Inches. You do this with all of the problems for example: The first one. Sue is 72 inches and Khalid is 54. Add them together and subtract them by 6 to get your final answer. Please DO NOT quote me on this lol. This is how I read the question. I think this is right but I am not absolutely 100% sure. Hope this helps.