Use percentage multipliers:
$28/0.8 = $35
The original price of the set is $35.
Hope This Helps!
To find your answer you must add them all together :
17,689
1,614
+ 176
_________
19,479
No solution for the quadratic equation because of the √-20
The rational root are x= 7,-3,-6
You can find them by substituting y for 0