Just 3 math problem show step by step

1 5x+y=-12
5x-7y=4

2. -5x+4y=-3
-9x-y=-30

3. -9x+6y=27
-x+3y=10
me out

What's for breakfast? all people who ate at a certain restaurant were surveyed as to what they ordered on a particular sunday morning. 40 ate eggs 42 ate sausage 32 ate pancakes 13 ate sausage and eggs 15 ate pancakes and sausage 11 ate eggs and pancakes 6 ate all three items 3 people didn't eat any of the items how many people ate only pancakes? how many people ate at the resturant that morning? how many people didn't eat eggs?