XZ = 8x - 18 Eq(1)
RZ = 2x+5 Eq(2)
First, we have to isolate X on Eq(1) and then R on Eq(2)
X= 8x - 18 / Z Eq(1)
R = 2x + 5 / Z Eq(2)
Then, multiply X by R:
[tex]\begin{gathered} \frac{8x-18}{Z}\cdot\frac{2x+5}{Z} \\ \frac{(8x-18)\cdot(2x+5)}{Z^2}\text{ (Multiplying fractions)} \\ \frac{16x^2+40x-36x-90}{Z^2}\text{ (Multiplying polynomials}) \\ \frac{16x^2+4x-90}{Z^2}\text{ (Operating like terms}) \\ \text{ Final Answer: XR=}\frac{16x^2+4x-90}{Z^2} \end{gathered}[/tex]
