Question

If y is 6 when x is 3 and y varies directly with x, find y when x is 8.

A. 4
B. 11
C. 16

Answer 1

\(\bf \begin{array}{cccllll}
\textit{something }&\textit{varies directly to }&\textit{something else}\\ \quad \\
\textit{something }&={\color{red}{ \textit{some value }}}&\textit{something else}\\ \quad \\
y&={\color{red}{ n}}&x&\implies y={\color{red}{ n}}x
\end{array}\\ \quad \\
y=6\qquad x=3\implies 6={\color{red}{ n}}(3)\)

find "n" or "constant of variation", then plug it in the equation y = nx

to find what "y" is when x = 8, well, just set x = 8 and solve for "y" :)