When a body is placed in a fluid, there is an upward force exerted on the body that is equal to the weight of the fluid displaced by it. When this force is equal to the weight of the body the net downward force acting on the body is zero and it floats in the fluid.
The block of ice that is placed on water has a density of 917 kg/m^3. The density of water is 1000 kg/m^3. If a fraction f of the volume V of the ice block is submerged in the water, f*V*1000*9.8 = (1 - f)*V*917*9.8
This gives f = 917/1000 = 0.917. The fraction of the block that is above the water is 1 - 0.917 = 0.083
The fraction of the ice block that floats on the water is 0.083