The driving force behind plate movement is the process of that occurs in the mantle

The given blank can be filled with convection currents.

The convection currents in the mantle. The heat from the centre of the earth causes the heating of the molten rock present in the mantle of the earth. This molten rock when comes to the lithosphere, it gets cool, which causes the formation of the convection current in the mantle. The plates are directly present above the mantle, and due to the production of the convection currents, the plates are moved.

multiplying and dividing the two decimals and the eqations by the same number of the overalls