Adding x days to a date depending on "Single Select" field

[Lawrence_Ames]

I am having a difficult time.

I have a “Single select field” called “Frequency” which is either labels ad Q3M or Q6M (which stands for every 3 months or every 6 months.
I have a “Last Contact” date field.
I am trying to add a "Next Contact formula column, which would take the “Last Contact” date and either add 90 or 180 days to the field, depending on the value of the “Single Select Field” of Q3M or Q6M

My formula, which does NOT work, is: DATEADD({Last Contact},if{Frequency}=“Q3M”,90,‘day’)

Help! I thnk I’m doing several things wrong but can’t figure it out. Also, not sure what the ‘day’ does. Thank you!

[Elias_Gomez_Sai]

Your IF is missing the parentheses. Also, I think it makes more sense to have the IF first and then the DATEADD.