Part 1
Pizzas sold last day = 65
Increasement needed in sale = 20%
pIzzas to be sold today
= 65 + 20% of 65
= 65 + 20/100 × 65
= 65 + 1/5 × 65
= 65 + 1/1 × 13
= 65 + 13
= 78
Part 2
Pizzas sold last day = 65
Pizzas sold today = 60
60 = 65 + x% of 65
60 = 65 + x/100 × 65
60 - 65 = x/20 × 13
- 5 = x/20 × 13
-5/13 = x/20
-5/13 × 20 = x
-7.692 = x
Therefore, there was a decrease in pizza sale by 7.692%
By rounding off,
The decrease in pizza sale was by 7.700%.
= 7.7%