Question

One half of the birds at the pet store are yellow. Tara buys one of the yellow birds. Then one third of the birds at the store are yellow. How many yellow birds were at the pet store before Tara bought one? Explain

Answer 1

$x - all\ birds\\ \\ \frac{1}{2} x \ -\ the\ yellow\ birds\\ \\ \frac{1}{2} x-1=\frac{1}{3} x\ \ /\cdot6\\ \\ 3x-6=2x\\ \\x=6\ \ \ \Rightarrow\ \ \ \frac{1}{2} x=\frac{1}{2} \cdot 6=3\\ \\ Ans.\ 3\ yellow\ birds$

Answer 2

Well, y=ny
2(y-1)=ny
(where ny is not-yellow)
You get y=2y-2 or y=2. You had two yellow birds and two other types.