First cake requires x cups of flour.
Second cake: x + 1/2
Third cake: 2x
2 pound bag has 8 1/2 cups and it's exactly what Carly needs, so we can write it down as:
8 1/2 = x + x + 1/2 + 2x
8 1/2 = 2x + 1/2 + 2x
8 1/2 = 4x + 1/2 / - 1/2 (both sides)
8 = 4x / ÷ 4 (both sides)
x = 2
Doublecheck:
2 + 2 + 1/2 + 2 * 2 =
= 2 + 2 + 1/2 + 4 =
= 4 + 1/2 + 4 =
= 8 + 1/2 =
= 8 1/2
It's the same, so it must be correct ;)
Answer: Carly needs 2 cups of flour for each cake.