Question

suppose y varies directly with x and y=1 when x=-3. What is the constant of variation? What is x when y=4?

Answer 1

\[\begin{align}y&\propto x\qquad\qquad\qquad&\\
\implies y&=kx&\text{k is an arbitrary constant}\\
\text{given: }y=1&{\rm when}\quad x=-3\\
\implies 1&=k(-3)\\
\boxed{1\over -3}&=k\\
\therefore y&={-1\over3}x\\
\end{align}\]
now you need to plug in y= 4 and solve for x