I need help with a few practice problems:

1.) 8x^-2 - 2x^-1 + 1 = 0

2.) Value of y?

-2x + 3z = 17

x - 2y - z = -3

-4x - 3y - z = 19

3.) Tasty Bakery sells three kinds of muffins: chocolate chip muffins at 15 cents each, oatmeal muffins at 20 cents each, and cranberry muffins at 25 cents each. Charles buys some of each kind and chooses twice as many cranberry muffins as chocolate chip muffins. If he spends $2.50 on 12 muffins, how many oatmeal muffins did he buy?