Can someone plz explain how to do this?

Write two subtraction equations that are equivalent to 5 + 12 = 17.

If g(x) is an odd function, which function must be an even function?

To solve the system of equations below, grace isolated the variable y in the first equation and then substituted into the second equation. what was the resulting equation? 3y=12x x^2/4+y^2/9=1