Calculate the mole fraction of ethanol(C2H5OH) in the solution containing 20g of ethanol and 100g of water?

Dear Shreya,
Mole fraction = moles of the component that is being identified for a mole fraction / total no. of moles 
moles of ethanol = 20 / molar mass of ethanol (46)
                           = 0.434
Moles of water = 100 / 18
                         = 5.556
total no. of moles = 5.556 + 0.434 
                            = 5.99 ~ 6.00
Mole fraction of ethanol = 0.434 / 6
                                       = 0.072 
Hope this is clear... :)