Transcript text: Let $x$ be the amount of 90 -octane gas used in the mixture. Complete the following chart.
\begin{tabular}{c|c|c|c}
Type of Gas & Quantity & $\%$ Isooctane & Amount of Isod \\
\hline 90 -octane & $x$ & $90 \%$ & $\square$ \\
99-octane & 400 & $99 \%$ & $\square$ \\
Mixture & $x+400$ & $94 \%$ & $\square$
\end{tabular}
(Simplify your answers. Use integers or decimals for any numbers in the expression.)