A baker knows that if he charges x dollars for a cake, he will sell $\displaystyle{20}-{x}\usepackage{cmbright}\Huge\$ of those cakes each week. So the total revenue for the cakes will be $\displaystyle{x}{\left({20}-{x}\right)}\usepackage{cmbright}\Huge\$ dollars. One week the baker's total revenue for these cakes was $84. How much did he charge for each cake, if it was less than $10?

The baker charged _____ dollars for one cake.