Another number puzzle

[Amethyst]

This one looks like algebra, only l can't remember how to set it up to find x. Can anyone help me?

 

[njhowie]

Started with $160.

Work from the end going backwards.

$35 + $10 = $45/.75 = $60
$60 + $15 = $75/.75 = $100
$100 + $20 = $120/.75 = $160

Now go forward to verify.

$160 * 25% = $40 + $20 = $60 from $160 = $100
$100 * 25% = $25 + $15 = $40 from $100 = $60
$60 * 25% = $15 + $10 = $25 from $60 = $35

 

[Amethyst]

Amazing. So, not algebra at all. I wouldn't have come up with that logic although I did try looking at it from the end vs. the start.