Let P = number of parrots and F = number of finches. According the problem we have;
P = 2 + 3F (1) and P + F = 18 (2) from the (2) we get P = 18 - F (3) subtracting (3) from (1) we have;
(1) - (3) = >>> 0 = -16 + 4F ==>>> 16 = 4F ==>>> F = 16/4 F = 4 putting where F = 4 to the (1)
we get; P = 2 + 3 *4 = 14. so we have F = 4 and P = 14