I am having trouble calculating vout/vin

 

you came up with

Vout = -(V1+V2)

Then

Vout/Vin = -(V1 + V2) / Vin

so, did you decide what voltage is Vin?

 

What is Vin?

Check your units. The last line of your work is not dimensionally consistent -- the left hand side (both left hand sides?) are dimensionless while the right hand side has units of voltage, so you KNOW it is wrong.