Standard Form is ax + by = c, where a, b, and c are not fractions and a is not negative.
So, you can go through each of your options to see which ones work with those rules.
A. 2.5x + 3y = 12 No, this is not in Standard Form. 2.5 can be rewritten as 2[tex] \frac{1}{2} [/tex], menaing A is a fraction, which you can't have.
B. -10x - 3y = 1 No, this is not in Standard Form. A is -10, but A can't be negative.
C. 2x + 3y = 12 Yes, this is in Standard Form. It follows all of the rules.
D. 5x + 5y = 10 Yes, this is in Standard Form. It follows all of the rules.
So, C and D are both written in Standard Form.
