Exclusive events, for OR we can add probabilities.
P(O or B) = 0.49 + 0.20 = 0.69
Answer 0.69
Given parameters:
Percentage gain = 300%
Selling cost last year = $2420
Unknown:
Selling cost this year = ?
Solution:
To solve this problem;
Profit percent = 
300 = 
3 = 
S- 2420 = 7260
S = $9680
To make a 300% gain, Jefferson Middle school needs a $9680 from fundraiser sales this year.
Im pretty sure it would be doubling the length of each side