Hello,
1 .65 + 0.20(65) = 65 + 13 = 78
(65 - 60) / 65 = 5/65 = 0.0769 x 100 = 7.69 rounds to 7.7 % decrease compared to the 65 pizza's sold yesterday
2. I posted a file to help you on this question!
3. Find principal by using the formula I=P⋅i⋅t, where I is interest, P is total principal, i is rate of interest per year, and t is total time in years.
So basically your answer is 600.
I truley hope this helps.
Have a good day!
-Jurgen