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<span>

, 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.
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Answer:
540 ft^2.
Step-by-step explanation:
The area of the trapezoid = h/2 (10 + 18) = 14h.
By Pythagoras the height h = √(5^2 - 4^2) = 3.
So the area of the 2 trapezoidal bases = 2 * 14*3
= 84 ft^2.
Now we calculate the area of the four lateral rectangular sides:
= 10*12 + 18*12 + 2*5*12
= 456 ft^2.
Total area = 456 + 54
= 540 ft^2.