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

$Y = 2(X-1)$


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


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