The Pappas family has two cats, Zeus and Athena. Together they weigh thirteen pounds. Zeus weighs 9 pounds. How much does Athena weigh?

Write an algebraic equation that represents the situation, use `a` (Athena's weight) for your variable.  

Athena weighs pounds.

Box 1: Enter your answer as an equation. Example: y=3x^2+1, 2+x+y=3
Be sure your variables match those in the question

Box 2: Enter your answer as an integer or decimal number. Examples: 3, -4, 5.5172
Enter DNE for Does Not Exist, oo for Infinity