Calculating the strength of electric force and gravitaional force

I have this problem with a question i need to do. The whole question is

Calculate how many times stronger the electric force is than the gravitaional force, between a proton of charge +e and mass Mp at a distance r from an electron of charge -e and mass Me given that:

e = 1.6 x 10 to -19 C
Me = 9.1 x 10 to -31 kg
Mp = 1.67 x 10 to -27 kg
Ke = 9.0 x 10 to 9 N M C
G = 6.7 x 10 to -11 N m kg

My problem is that the only 2 equations i can think of using for it are coulombs law and newtons law of gravity. The trouble is i dont know r, so i cant simply calculate them out. There's also no point i think in rearranging the formulas for r to find it since i dont know F in either case.

Totally stuck on this, is there another equation that i may have overlooked that i could use? Or maybe something else im overlooking? Any help appreciated.