jmc

Make a table to organize the information about the cost and the volume of the three tubes of toothpaste. Let the number of units of volume in one tube of Fresh be $u$. Then the cost of one tube of Fresh is \u$.SinceBrightismoreexpensivethanFreshby$60\%$,onetubeofBrightcosts$\$\frac{8}{5}u$. Also, since Glow has $33\frac{1}{3}\%$ more volume than Fresh, the volume of a tube of Glow is $\frac{4}{3}u$ units. $$\begin{array}{ccc}& \text{volume}& \text{cost}\\ \text{Bright}& & \$\frac{8}{5}u\\ \text{Fresh}& u& \$u\\ \text{Glow}& \frac{4}{3}u& \end{array}$$Finally, multiply the volume of Glow by $\frac{3}{4}$ to find the volume of Bright, and multiply the cost of Bright by $\frac{3}{4}$ to find the cost of Glow. $$\begin{array}{ccc}& \text{volume}& \text{cost}\\ \text{Bright}& u& \$\frac{8}{5}u\\ \text{Fresh}& u& \$u\\ \text{Glow}& \frac{4}{3}u& \$\frac{6}{5}u\end{array}$$Dividing the cost of a tube of Glow by its volume, we find a cost-per-unit-volume of \\frac{6}{5}u\div \frac{4}{3}u=\$\frac{9}{10}=\boxed{90}$ cents.