This is the locations of oil deposits problem.. HELLLPPP...!!!!?

There's no way I would do your problem step-by-step, that's for you to do, but you have the density and you can calculate the volume of each sphere, so you can calculate the "mass" of each sphere, although in the case of the anomaly that mass will be negative. Essentially it acts like a sphere with density 900-5500 = -4600 kg/m^3. Determine the gravitational acceleration generated by each on the Earth's surface. They act just like two point masses, one with center at the center of the Earth and the other with center at the center of the anomaly and you can calculate the gravitational force per unit mass due to each (that is, the acceleration) and take the ratio of that to what there would be with no anomaly.