If a problem states "$y$ is directly proportional to $x$," what can you immediately infer about $y$ when $x=0$?

Given the direct variation $y=\frac{3}{4}x$, solve for $x$ when $y=12$.

The time $T$ required to complete a fixed project varies inversely with the number of workers $n$. If $8$ workers complete the project in $15$ hours, how many workers are needed to finish the project in $10$ hours?