OG详解-OG7 数学1 Q41

The correct answer is 87. It’s given that in August, the car dealer completed 15  more than 3 times the number of sales the car dealer completed in September.  Let x represent the number of sales the car dealer completed in September. It follows that 3x+15 represents the number of sales the car dealer completed in August. It’s also given that in August and September, the car dealer completed   363 sales. It follows that x+(3x+15) = 363, or 4x+15 = 363. Subtracting 15  from each side of this equation yields 4x = 348. Dividing each side of this equation by 4 yields x = 87. Therefore, the car dealer completed 87 sales in September.