Answer :

15 ÷ 10 
15 ÷ 0.1 
150

15 is 10% of 150
-----------------------------------
18 ÷ 60 
18 ÷ 0.6 
30

18 is 60% of 30
10x/100=15
x/10=15
x=15·10
x=150

60x/100=18
3x/5=18
3x=18·5
3x=90
x=30