Density of air fuel mixture

ncr7

I know this is a really simple calculation but I can't figure out how to find the density of the mixture for some reason. Density of the fuel is .67 kg/m^3 and air is 1.2 kg/m^3 and fuel to air ratio is .1705. Is it just .1705*1.2 kg/m^3 + .67 kg/m^3 = .8746 kg/m^3.

Just working on an experiment and I guess I'm to tired to figure this one out right now by myself haha. Thanks for your help in advance.