[tex]\\
\text{The store pays }\$35 \text{ for a fish tank.}\\
\text{and the markup is }20\% \text{ of }\$35\\
\\
\text{so first we find the markup as}\\
\\
=20\% \text{ of }\$35\\
\\
=0.20\times 35\\
\\
=7\\
\\
\text{hence the selling price of fish tank}=\text{Cost of store + Markup}\\
\\
\Rightarrow \text{selling price}=35+7\\
\\
\Rightarrow \text{selling price}=42[/tex]
Hence the selling price of the fish tank is $42
