The given question would form a simultaneous equation.
Let the cost of a movie be "x" and the cost of a video game by "y."
Therefore, when Brian rented 7 movies and 9 video games for a total of $78, this would form this equation.
[tex]7x+9y=78-------\mleft\lbrace1\mright\rbrace[/tex]When Brian rented 5 movies and 3 video games for a total of $36, this would give
[tex]5x+3y=36--------\mleft\lbrace2\mright\rbrace[/tex]To solve the simultaneous equation we need to create equation three and use the elimination method to eliminate one variable.
We would multiply equation two by 3 to get equation three
[tex]\begin{gathered} 3(5x+3y=36) \\ 15x+9y=108-----\mleft\lbrace3\mright\rbrace \end{gathered}[/tex]The next step would be to subtract equation two from equation three
[tex]\begin{gathered} 15x-7y+9y-9y=108-78 \\ 8y=30 \\ y=\frac{30}{8} \\ y=3.75 \end{gathered}[/tex]We would then substitute the value of "y" into equation two to get "x."
[tex]undefined[/tex]