You can solve a system with variables by:
1. Pick any two pairs of equations from the system.
2. Eliminate the same variable from each pair using the Addition/Subtraction method
3. Solve the system of the two new equations using the Addition/Subtraction method
4. Substitute the solution back into one of the original equations and solve for the third variable
5. check by plugging the solution into one of the other three equations
She can make 12 different combinations.
If she used three different colors for the keychain, there's still 4 other colors left.
4 x 3 = 12
The answer is A. The Associative Property, followed by the Associative Property.
It's because they want you to group stuff, not simplify them.
