Out of the 500 marbles that Cindy had, she gave her four friends 80 marbles each. What's four times the number of marbles she has remaining?
Cindy gave her four friends 80 marbles each, a total of 4*80 = 
<gadget id="calculator">80*4</gadget>
<output>320</output>
320 marbles.
She was left with 500-320 = 
<gadget id="calculator">500-320</gadget>
<output>180</output>
180 marbles.
Four times the number of marbles she has remaining is 180*4 = 
<gadget id="calculator">180*4</gadget>
<output>720</output>
720.

<result>720</result>