In collection of animals including birds and beasts they had 43 heads 120 feets. How many are there in collection?

Let the number of birds be \(x\) and the number of beasts be \(y\).

Then

$$x + y = 43$$

and

$$2x + 4y = 120$$

Solving these equations by substitution,

$$2x + 4(43 - x) = 120$$

$$2x + 172 - 4x = 120$$

$$-2x = -52$$

$$x = 26$$

$$y = 43 - 26 = 17$$

Therefore, there are \(26\) birds and \(17\) beasts in the collection.