Does

2 3/4 cups of flour
2 cups of sugar
1 teaspoon of baking powder
1 1/4 cups of butter
2 teaspoons of extract
2 eggs

Make 30 cookies

Yes,

Why is it correct

Why not. In my experience baking cookies, that's enough for 30 cookies. You haven't specified the size of each cookie.

If you don't believe me, try it yourself.

Thank you can I ask another question

Sure.

Does

1 1/2 cups of flour
3/4 cups of sugar
1 1/2 teaspoon baking powder
1/3 teaspoon salt
3/4 cups of milk
3/4 cups of butter
6 teaspoons extract
3 eggs

How much cupcakes can this make

I don't know.

I suggest you search online for cupcake recipes and see which come the closest to your amount of flour, milk and eggs.