is this question correct?

Tiffany, pense-tu Monica est intelligent?

check ending of tu form.

Monica is intelligent. What is feminine adjective ending?

im pretty sure since monica is a girl it should be intelligente. but other than that i think it is good.

oops sorry i didn't see abby had already posted ^^

Tiffany, penses-tu que Monica est intelligente?

Tes, the ending on the verb penser is -s, you need clause relater "que" and Monica (Monique) es feminine.

Sra (aka Mme)

The question you provided seems to be a combination of English and French. The correct way to ask this question in French would be: "Tiffany, penses-tu que Monica est intelligente ?"