The common expressions supposed to meaning “meant to” or “intended to” and used to meaning “formerly” are frequently misspelled or misunderstood.
Both expression are normally in the Passive Voice. This means that the verb is the past participle so it ends with an -ed. Writers sometimes drop the final d because of the t sound which follows it.
Incorrect: We are suppose to meet at seven.
Correct: We are supposed to meet at seven.
Incorrect: I use to read every Hardy Boys book I could find.
Correct: I used to read every Hardy Boys book I could find.