$con = Get-Content .\test.txt
$x = $con.IndexOf(136)
$y = $con.IndexOf(228)
$z = $con.IndexOf(579)
[string]$n = $con.IndexOf(893)
$a = $x + $y
$a
$b = $x * $z
$b
$c = $x - $z
$c
$($x + $y) * $($z - $x) + $($y + $z)
$g = $con.Length - $n.Length
$g