ANSWER
8 minutes
EXPLANATION
We know that the cost of using the internet in dollars is given by,
[tex]y=\frac{3}{4}x[/tex]Where x is the number of minutes spent on the internet.
In this problem, we have to find how many minutes will 6 dollars buy. In other words, we have to find x for y = 6. To solve the given equation for x, we have to multiply both sides by 4,
[tex]\begin{gathered} 4y=4\cdot\frac{3}{4}x \\ \\ 4y=3x \end{gathered}[/tex]And divide both sides by 3,
[tex]\begin{gathered} \frac{4y}{3}=\frac{3x}{3} \\ \\ \frac{4y}{3}=x \end{gathered}[/tex]So, for y = 6, x is,
[tex]x=\frac{4\cdot6}{3}=\frac{24}{3}=8[/tex]Hence, $6 will buy 8 minutes.