From the rectangle 1 3 take away the same square A, and what rectangle remains?
Which is greater, the rectangle B, or the rectangle C?
What same thing did we take away from equals?
From what did we first take it?
What remained?
From what did we next take it?
What remained?
What did we find true of the two remainders?
If the same thing be taken from equals, the remainders will be equal.