I use those variables in the second xy+z and i got this
<span><span>−<span><span>12<span>x^2</span></span>z</span></span>+<span><span>12y</span>z</span></span>+<span>4</span>
Given that 15 is more than a number x, we can represent it by the following inequality:
x < 15
Hope that helped =)
The answer is 1 because 2 times 2 + 4 is 8