So 18 oranges are 12 percent of her total oranges. You can use Ratio to solve this.
O : P
18 : 12 P = Percentage O = Orange
1.5 : 1
150 : 100
All I did was make the percentage one by dividing both numbers by 12. This makes it 1.5 oranges per percent. Times 1.5 with 100 to make it 100 percent.