The number of crates of apples left is 90 - 72 = 18
90 crates of apples represent 100%.
To find what percent represent 18 crates of apples, we can use the next proportion:
[tex]\frac{90\text{ crates of apples}}{18\text{ crates of apples}}=\frac{100\text{ \%}}{x\text{ \%}}[/tex]Solving for x:
[tex]\begin{gathered} 90\cdot x=100\cdot18 \\ x=\frac{1800}{90} \\ x=20 \end{gathered}[/tex]20 % is left
