ANSWER
x = -24
EXPLANATION
We have that y = 12 when x = 18.
To solve this we have to use the ratio of y to x.
We have that y : x is:
12 : 18
We also have:
-16 : x
Since the ratios are equal to y : x, we have:
[tex]\begin{gathered} 12\text{ : 18 = -16 : x} \\ \Rightarrow\text{ }\frac{12}{18}\text{ = }\frac{-16}{x} \\ \text{Cross}-mu\text{ltiply:} \\ 12\cdot\text{ x = -16 }\cdot\text{ 18} \\ x\text{ = }\frac{-16\cdot\text{ 18}}{12} \\ x\text{ = -24} \end{gathered}[/tex]That is the value of x.
