Ineed on this problem
20 ÷ (4 - (10 - 8))

10

Explanation:

20 ÷ (4- (10-8))

First off, you work your way outward. You start the furthest in, then head your way out. (10 - 8) is the furthest in, and 10 - 8 = 2. So now your equation looks like this:

20  ÷ (4 - 2)

Next, you do the (4 - 2) which equals 2. So now, the equation is this:

20  ÷ 2

So you finish it up with 20  ÷ 2 which equals 10.

Hope I made sense! :D