NoLifeLeft wrote:But you have only 2 Hourglasses, one measures 7-minutes, and the other measures 4-minutes. How can you correctly measure 9 minutes?

Start the 7 and 4 together, when the 4 runs out, the 7 will have 3 left.

Flip the four, when the 7 runs out, there'll be one left on the 4. Start the egg.

Once the four's done, flip twice for 8 more.