STEP - BY - STEP EXPLANATION
What to find?
Percentage change.
Given:
original quantity = $30
New quantity = $39
Step 1
Recall the formula for percentage change.
[tex]\text{ \% change=}\frac{new\text{ quantity-original quantity}}{original\text{ quantity}}\times100\text{ \%}[/tex]Step 2
Substitute the values.
[tex]\text{ \% change=}\frac{39-30}{30}\times100\text{ \%}[/tex][tex]=\frac{9}{30}\times100^\text{ \%}[/tex][tex]=30\text{ \%}[/tex]Hence, we have a 30% percentage increase.
ANSWER
C. 30%