100ml of water sample during titration consumes 8ml of 0.02 M EDTA.calculate hardness of water

Do you know what makes water hard?

What substance in the water will react with EDTA. Do you know the equation for the reaction taking place?

That's basically what you need to know. All the other things are only calculations and proportions mainly.

Find the number of moles of EDTA, then the corresponding number of moles of the substance in water, then work out its concentration in water to finally work out get the hardness of the water sample.