Ernise evaluated the expression $\displaystyle{10}{\left({3}+{5}\right)}\usepackage{cmbright}\Huge\$ like this:

Step 1: $\displaystyle{10}\cdot{3}+{10}\cdot{5}\usepackage{cmbright}\Huge\$

Step 2: $\displaystyle{30}+{50}\usepackage{cmbright}\Huge\$

Step 3: 80

Which mathematical property was she using?