### Home > PC > Chapter 12 > Lesson 12.2.2 > Problem 12-55

12-55.

In general,

Set up a system of equations and solve for *y* in terms of *x*.

For parts (c), (d), and (e), follow the steps in part (b).

Solving for *x* in the top equation and *y* in the bottom equation:

By substitution:

*x*(*k* + 4)(*k* − 7) = −30*x*

Since we have assumed *x* ≠ 0, divide by *x* and solve for *k*.