Chapter 11 - Polynomial and Rational Functions - 11.1 Power Functions and Proportionality - Exercises and Problems for Section 11.1 - Exercises and Problems - Page 440: 23

$x=5.33$ when $y=8$

We are given $y=6; x=4$ $y$ is directly proportional to $x$. We can write $y=kx~~~~(1)$ Plug $y=6, x=4$ in equation (1) to obtain: $6=k (4) \implies k=\dfrac{3}{2}$ Thus, we have: $y=\dfrac{3}{2}x ~~~~(2)$ Now, plug $y=8$ in Equation (2) to obtain: $8=\dfrac{3}{2} x \implies x=5.33$ Therefore, we get $x=5.33$ when $y=8$.