<span>Find
the number of bluejays bird and robins birds as joan counted it
=> the number of Robins is twice as bluejay
=> Robins = 2X
=> The number of bluejay is about to know:
=> Bluejay = X
The total number of birds is 21.
=> 2X + X = 21
=> 3x = 21
=> 3x / 3 = 21 / 3
=> x = 7
Thus the number of bluejay is 7
=> Robin = 2(7)
=> Robin = 14
Thus the number of Robin is 14</span>