Hello !

As given in the question, a solution of ethylene glycol and water contains 20% of ethylene glycol by mass.

That is, in 100g of solution -  20g of ethylene glycol.

Molar mass of ethylene glycol - (12*2  + 1*6 + 16*2) = 62g/mol.

so, in 20g we have 20/62 = 0.32 mol.

remaining 80g contains water. Number of moles of water = 80/18 = 4.44 mol

Mole fraction of ethylene glycol = No of moles of ethylene glocal/ Total number of moles.

= 0.32/(0.32 + 4.44)

= 0.068 .

Mole fraction of water = 1-0.068 = 0.932