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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Cos 28 = 18/ y
so
y = 18 / cos 28
y = 18 /.8829
y = 20.4
You remember from SOH CAH TOA that
.. Cos = Adjacent/Hypotenuse
.. cos(C) = 80/82 = 40/41 . . . . . . . . . . . seems to match the last selection
The factors of 44 are: 1, 2, 4, 11, 22, 44
The factors of 66 are: 1, 2, 3, 6, 11, 22, 33, 66
Then the greatest common factor is 22.
Just a regular pentagon has 5 sides. and also has 5 lines of symmetry.
So if a shape has 7 sides it will have 7 lines of symmetry.
Its always going to be the same number.
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