To solve the equation [tex]\( 5a = 15 \)[/tex] and find the age of Frank, we need to isolate the variable [tex]\( a \)[/tex]. Let's go through the steps to do this.
1. We start with the equation:
[tex]\[ 5a = 15 \][/tex]
2. To isolate [tex]\( a \)[/tex], we need to undo the multiplication by 5. The way to do this is by dividing both sides of the equation by 5:
[tex]\[ \frac{5a}{5} = \frac{15}{5} \][/tex]
3. Dividing both sides by 5 simplifies the equation to:
[tex]\[ a = 3 \][/tex]
So, Frank is 3 years old.
The correct choice from the options given is:
c. Multiply both sides of the equation by [tex]\(\frac{1}{5}\)[/tex].