multiply percentage (Using Codeigniter 3)

I have 3 echo values that I need to multiply percentage directly on a view page:
$x1
$x2
$x3

Example:
$x1 = 1000
$x2 = 50
$x3 = 10
The following should be calculated:
x1 * x2 as% * x3 as%
Sum of this Example = 50


How should the calculation be with echo on the view-page?