3. Suppose that $y=a x+(1-a)$ for some unknown number $a$. If $x=3$, the value of $y$ is 7 . Then, if $x=8$, what is the value of $y$ ?
3. Since $x=3$ and $y=7$ satisfy the given relation $y=a x+(1-a)$, then $7=3 a+(1-a)$ or $7=2 a+1$.
Thus, $2 a=6$ and so $a=3$.
When $x=8$, we therefore obtain $y=a x+(1-a)=3(8)+(1-3)=24-2=22$.
ANSWER: 22