A truck driver drove for 2 days. On the second day, he drove 3 hours longer and at an average speed of 15 miles per hour faster than he drove on the first day. If he drove a total of 1,000 miles and spent 21 hours driving during the 2 days, what was his average speed on the first day, in miles per hour?
Choose the correct choice from the following choices
A) 25 B) 30 C) 35 D) 39 E) 45
39ay 1   2t+3=21   t=9   39ay 2   t+3   9+3= 
<gadget id="calculator">9+3</gadget>
<output>12</output>
12   9r+12(r+15)=1000   r=39   Answer:39
<result>D</result>
A truck driver drove for 2 days. On the second day, he drove 3 hours longer and at an average speed of 15 miles per hour faster than he drove on the first day. If he drove a total of 1,000 miles and spent 21 hours driving during the 2 days, what was his average speed on the first day, in miles per hour?