So 15% is out of 100%, and the cab company has sent 30 cabs out of x?(x is the total number of cabs). 
So, by setting up that data we already know, we can make this equation to figure out how many cabs total the company actually has:
<span>15x = 100 * 30
</span>
We do the multiplication on the right side
15x = 3000
And divide to isolate the "X" variable
x = 200
So, the cab company has 200 cabs total, and they sent out 30 of them.
So, by setting up that data we already know, we can make this equation to figure out how many cabs total the company actually has:
<span>15x = 100 * 30
</span>
We do the multiplication on the right side
15x = 3000
And divide to isolate the "X" variable
x = 200
So, the cab company has 200 cabs total, and they sent out 30 of them.