Answer:
10 minutes
Explanation:
Since you can do 6 flyers each minute, the rate would go at 6x, with x being minutes. You initially did 80, so the equation for you would be y=6x+80.
Your friend's equation would be y=4x+100, because he initially had 100 done and is now getting 4 done per minute.
If you put the 2 equations in your calculator, the intersection will happen at x=10, showing that you and your friend will have an equal number of flyers at 10 minutes.