If the 2017 agi must match, how do I do that if I had no agi since I could be and was claimed under my mothers name how could the irs have number on file for me?

People who are claimed as dependents on someone else's return can -- and sometimes are required to -- file income tax returns, so it's not really relevant that you're claimed as a dependent.

That said, if you filed a return last year, you should have an AGI. Please see the TurboTax FAQ "How do I find last year’s AGI?" for guidance.

https://ttlc.intuit.com/replies/3301618

If you didn't file a return last year, please see the TurboTax FAQ "What do I put for my AGI if I didn't file last year?" below for guidance.

https://ttlc.intuit.com/replies/4231698