REMAINDER money, after losses 20% of his money 
= N - 20% of N 
= N - (N x 20)/100 
= (5N - N)/5 
= 4N/5 
Remainder money, after spending 25% of his remainder money 
= 4N/5 - 25% of (4N/5) 
= 4N/5 - (4N/5) x (25/100)
= 4N/5 - N/5 
= (4N - N)/5 
= 3N/5
 
According to the QUESTION, 
3N/5 = 480
  x = 480 x 5/3 =   800