First off, when you replace a variable with a number, you <em>have</em> to put it in parenthesis.
If x=2 and y=4, the equation would look like this:
4(2) × 8(4)
If we remember PEMDAS, parenthesis comes first. Meaning you have to multiply 4 and 2 first (because you always go from left to right when you have two of the same operation). Then , the expression would look like this:
Step-by-step explanation: You can set up the equation: = You square both sides to cancel out the squares which leaves you with = n - 4. Then you just solve as normal which ends you up with an answer of 6. You can check this by plugging 6 back into the equation and see that you end up with on both sides.