Chapter 5 - Linear Functions - 5-1 Rate of Change and Slope - Practice and Problem-Solving Exercises - Page 297: 43

$y=6$

This is because of the slope. Because our slope is $3$, we're going to rise by $3$ points and run by $1$. So, if we are starting from $(4,3)$ and the $x$ value of our next point is $5$, that means we already ran by $1$. Now, we just need rise by $3$, so that will be added to our $y$ value of $3$. This would make our new point $(5,6)$.