Answer:
39
Explanation:
Let, total rooms girls booked be x and total rooms girls booked be y.
entire hotel was booked except two rooms.
so, total = 158-2 = 156
x+ y = 156
this is equation 1.
also, girls are using three times more room than boys.
so, y=3x
substituting y=3x in 1st equation,
x+ 3x = 156
or, 4x = 156
or, x= 156/4
x= 39