Answer:
A.
Step-by-step explanation:
Let the number of the birds apart from the newcomer, be x.
x/2 + 1 = 100
which means,
x/2 = 100 - 1,
this gives us a 99.
x/2 = 99.
To get the actual number and kill the fraction we multiply by 2.
x = 2 x 99
...
x= 198...
Therefore,
The total birds flying were 198.
PROOF:
198/2 = 99.
99+ 1 = 100.
That one added to the 99 is the newcomer bird.