We can say that the amount of tables borrowed is x, chairs borrowed is y, and total borrowed is z. By the 2nd sentence we can say 3x=y. And assuming every table and chair has 4 legs, we can also say that 4x+4y=80. Using substitution, we can then say that 4x+12x=80, and 16x=80, which simplifies to x=5. Plugging x back in, we get 3*5=y=15. So than x + y is the total, or 5+15, so the answer is 20.
