Explanation:
she is the only sales agent selling cars after totaling them ... :-)
she makes 12% commission on the amount of sales beyond $50,000.
so, total sales was $115,000.
the base for her commission is then
115,000 - 50,000 = $65,000
she gets 12% of these $65,000.
100% = $65,000
1% = 100%/100 = 65,000/100 = $650.
12% = 1%×12 = 650 × 12 = $7,800
so, C is the right answer.