Duolingo being a dick: https://www.dropbox.com/s/7tm1b28cqlbh1fy/cuentanonmigo.png?dl=0
Cuenta conmigo :) It depends on the context
"Contar con" is an expression (that we learned a while back in Duo) that means "to rely/count on." "Cuenta," as used here, is the 2nd person (tú) Imperative/Command form of "contar." Since we haven't learned the Imperative yet, this is kind of an unfair sentence here. "Tú puedes contar conmigo" would have been better.
The translation in the question states: "You can count with me." (Where does the "can" come from). Entirely different than what it states here: "Count on me." Neither appears to be the correct translation with is "Count with me". DL: The inconsistencies that have arisen since the change in format are very frustrating and not conducive to learning.