"You have to pay the interest."
Translation:Tienes que pagar los intereses.
One: Check your entire sentence just in case something else was wrong. By the by, apparently, Duo has been marking "el interes" (singular) wrong, another matter under dispute.
Two: Part of it is Duo, part of it is Spanish. Spanish regularly allows the omission of personal pronouns, especially "yo," "nosotros," "tu," and "usted(es)." So, no, it is usually not apparent from Duo's exercises what is specifically meant. Verb conjugations may well be the only context or clue we are given.
That's the bad news. The good news is, if you're consistent in your usage of pronouns and verb conjugations, Duo usually lets it pass.
- You probably mean usted. But hating to pay interest rates is kind of understandable, too.
- tiene que or necesita (without que)
- As I understand it, el interés is the interest rate, while los intereses is the interest amount. Most of us pay the amount, which might explain why el interés is not accepted here.