The x's are all variables. Any numbers following variables must be exponents and should be preceded by a caret but that's okay. Bearing that in mind:
1. 7x^3y^3 + 3x^2y^2 + 12
From first post: 7x3y3 + 3x2y2 + 12
2. 4x^2 – 2x + 2
From first post: 4x2-2x+2
3. 12x^5 – 48x^3 + 30x^2
From first post: 12x5 - 48x3+30x2
Sorry if I'm wrong. Math isn't my forte. (Last year I took AP Statistics, AP math for idiots; I don't think I've done real math for ages lol.)