Let $\displaystyle{t}=\usepackage{cmbright}\Huge\$ the time, in hours, it takes the owner to frame one poster. Then $\displaystyle{4}{t}=\usepackage{cmbright}\Huge\$ the amount of time it takes the apprentice. Their rates are $\displaystyle\frac{{1}}{{t}}\usepackage{cmbright}\Huge\$ and $\displaystyle\frac{{1}}{{{4}{t}}}\usepackage{cmbright}\Huge\$ posters per hour. You may have added these fractions incorrectly when finding their combined rate. To add two fractions, you must rewrite one or both so that they have a common denominator.