Brenda can buy a used motorcycle for $1500 cash, or she can pay a down payment of 10% and make 24 monthly payments of $64.80. What is her finance charge if she chooses the second option?

The amount of the down payment is $1500 x 10/100 = $<<1500*10/100=150>>150.

So, the amount Brenda will finance is $1500 - $150 = $<<1500-150=1350>>1350.
Hence, the total cost of the motorcycle if Brenda chooses the second option is $1350 + (24 x $64.80) = $<<1350+(24*64.8)=3007.20>>3007.20.
Therefore, Brenda will pay a finance charge of $3007.20 - $1500 = $<<3007.20-1500=1507.20>>1507.20. Answer: \boxed{1507.20}.

To calculate the finance charge for Brenda's second option, we need to determine the total cost of financing.

First, let's calculate the down payment:
Down Payment = 10% of $1500
Down Payment = 0.10 x $1500
Down Payment = $150

Next, let's calculate the amount that Brenda is financing:
Amount Financed = $1500 - $150 (down payment)
Amount Financed = $1350

Now, let's calculate the total amount repaid over 24 months:
Total Amount Repaid = Monthly Payment x Number of Payments
Total Amount Repaid = $64.80 x 24
Total Amount Repaid = $1555.20

Finally, let's calculate the finance charge:
Finance Charge = Total Amount Repaid - Amount Financed
Finance Charge = $1555.20 - $1350
Finance Charge = $205.20

Therefore, Brenda's finance charge for the second option is $205.20.