Sarah starts saving $5.00 a week for 4 weeks.  Then she saves $10.00 a week for the next 4 weeks.  Then she saves $20.00 a week for the next 4 weeks.  How much money has she saved over 12 weeks?
She starts with $5.00 a week for 4 weeks so that's 5*4 = $
<gadget id="calculator">5*4</gadget>
<output>20</output>
20.00.
Then she bumps it up to $10.00 a week for 4 weeks so that's 10*4 = $
<gadget id="calculator">10*4</gadget>
<output>40</output>
40.00.
After that, she saves $20.00 a week for 4 weeks so that's 20*4 = $
<gadget id="calculator">20*4</gadget>
<output>80</output>
80.00.
Over 12 weeks she has saved 20+40+80 = $
<gadget id="calculator">20+40+80</gadget>
<output>140</output>
140.00.

<result>140</result>