Hey there!!
Jason = 800 + Paul
Alex = Jason - 150
How much more does Alex have the Paul?
Let's take the equation of Alex
... Alex = Jason - 150
... Add 150 on both sides
... Alex + 150 = Jason
Now we have the equation for Jason,
... Jason = 800 + Paul , and we got Alex + 150 = Jason
... Now let's plug in the values
... Alex + 150 = 800 + Paul
Subtract 150 on both sides...
Alex = 800 - 150 + Paul
... Alex = 650 + Paul
Now we got the answer for our question :
The answer - Alex has $650 than Paul.
Hope my answer helps!!