Fibonacci posed the following problem:
A man whose end was approaching summoned his sons and said: "Divide my money as I shall prescribe."
To his eldest son, he said, "You are to have 1 gold coin and 1/7 of what is left."
To his second son he said, "Take 2 gold coins and 1/7 of what remains."
To the third son, "You are to take 3 gold coins and 1/7 of what is left."
Thus he gave each son 1 gold coin more than the previous son and 1/7 of what remained,
and to the last son all that was left.
After following their father's instructions with care, the sons found that they had shared their inheritance equally.
How many sons were there, and how large was the estate?