Absolute value is when you have either a positive or negative value within a set of "parentheses" or what look just like vertical lines and whatever is within those line stays or becomes positive. The only exception to this is when there is a negative on the outside to act upon the positive values within.
Answer:
The system that can be used is:


Step-by-step explanation:
We have that:
x is the price of a package of sugar cookies, y is the price of a package of oatmeal cookies.
Shaikha sold 10 packages of sugar cookies and 2 packages of oatmeal cookies for $56.
This means that:

Khalid sold 9 packages of sugar cookies and 3 packages of oatmeal cookies for $60.
This means that 
System that can be used:
The system that can be used is:


120/143. 12 x 10 is 120, and 13 x 11 is 143. It is already in simplest form.