try this:
apply voltage divider at the + input of the op amp V+ = ...
assuming a perfect op amp, V- and output = V+
combine R25 and R28 to one equivalent resistor
assuming Vo is open, apply voltage divider (Vf, R21, V+ and equivalent R25-R28)
when you have Vo = ..., replace V+ with what you got above
follow the rules of algebra
expand everything so there are no parenthesis and no fractions
put all terms with R37 on one side of =, everything else on the other side
factor out R37 and divide