Answer:
B. 58 - b
Step-by-step explanation:
58 goes in the front, since that is how many birds were there at the start. If B birds flew away, then some are leaving which means the equation would be subtracting by B.
5
5(a+3)=40
5a+15=40
5a+15-15=40-15
5a=25
a=5
100 square feet