Carol gets a fixed $20 allowance each week. She can also earn $1.5 more dollars each week if she does extra chores. At the end of 10 weeks, she has 425 dollars. How many extra chores did she average each week?
She earned $42.5 on average per week because 425 / 10 = 
<gadget id="calculator">425/10</gadget>
<output>85/2 = around 42.5</output>
42.5.
She earned $22.5 each week from extra chores because 42.5 - 20 = 
<gadget id="calculator">42.5-20</gadget>
<output>22.5</output>
22.5.
She did 15 extra chores a week because 22.5 / 1.5 = 
<gadget id="calculator">22.5/1.5</gadget>
<output>15</output>
15.

<result>15</result>