Greek Anthology Book XIV: Metrodorus: 136

Arithmetical Epigram of Metrodorus
Brick-makers, I am in a great hurry to erect this house To-day is cloudless, and I do not require many more bricks, but I have all I want but three hundred. Thou alone in one day couldst make as many, but thy son left off working when he had finished two hundred, and thy son-in-law when he had made two hundred and fifty. Working all together, in how many hours can you make these?

Solution
Let $b$ be the number of bricks they can produce together in one day.

Then:

Thus it takes $\dfrac {300} {750} = \dfrac 2 5$ of a day to produce $300$ bricks when all working together.