Answer:
Deandra completed the first 6 problems at a rate of 3 problems per hour and the last 12 at a rate of 4 problems per hour.
Step-by-step explanation:
6 problems ÷ 2 hours = 3 problems per hour
12 problems ÷ 3 hours = 4 problems per hour
<em><u>4(10+9) - 40 + 36</u></em>
<em><u>9(5+2) - 45 + 18</u></em>
<em><u>3(12+7) - 36 + 21</u></em>
hope this helps you ...