# How many trees and birds are there? [closed]

There are 'X' number of Trees and 'Y' number Birds.

• If 1 bird sits on each tree then 1 BIRD will be left.
• If 2 birds sits on each tree then 1 TREE will be left.

What is number of trees(X) and birds(Y)?

## closed as off-topic by Omega Krypton, Gareth McCaughan♦Feb 18 at 12:14

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There are

$$4$$ birds and $$3$$ trees

The first equation means that

$$Y = X+1$$

The second equation means that

$$Y = 2(X-1)$$

Hence

$$2(X-1) = X + 1 \Rightarrow X = 3 \Rightarrow Y=4$$