Answer:
12
Explanation:
Let the mass of such 60 books be x
150/30= 60/x
Cross multiply both sides
150 × x= 30×60
150x= 1800
Divide both side by the coefficient of x which is 150
150x/150= 1800/150
x= 1800/150
= 12
Hence the mass of such 60 books is 12kg
