Answer:
-5
Step-by-step explanation:
mark brainlest plzzz
The mean is the average of a set of numbers, to find the mean, add all the numbers, then divide by the amount of numbers.
I’m not rly sure what it means by flipping the card …. I’m assuming there’s more to this question but if it’s what I think it is the only way this equation will be true is by switching the + Symbol to - (subtraction) which would be 1-2= 3-4 since it would 1=1 making the equation true