For a certain bathtub, the hot water faucet can fill the tub in 13 minutes. the cold water faucet can fill the tub in 12 minutes. if both faucets are used together, how long will it take to fill the tub?

This is a rational expression because the denominator contains a variable. this is a polynomial with 3 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 4 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 4 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 3 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 5 terms.