Answer:
B. 
Step-by-step explanation:
Let l represent length of rectangle and w represent width of rectangle.
We have been given four formulas for the perimeter of rectangle. We are asked to choose the formula that displays a common student error for finding the perimeter.
We know that perimeter of a polygon is sum of all sides of the polygon. We also know that rectangle is polygon having two sets of equal sides.
The perimeter, P, of rectangle will be sum of its all sides that is:

Combine like terms:

Factor out 2:

Upon looking at our given choices, we can see that formula represented by option B displays a common student error for finding the perimeter.
Standard form is just putting (in this case) variables in alphabetical order. First we simplify- 2x+4=4y would become 1/2x+1=y. This is already in standard form, as numbers w/o variables come at the end. simplifying the next one is more tricky. first you get a variable/number alone-
9-2x-2y=4x+3
9-2y=6x+3
6-2y=6x
1-1/3y=x
1=x+1/3y
3=x+y
x+y=3
sorry if I was wrong and not of any help, But I do believe this is correct.
150/200×100%=75%
75% of 200 miles is 150 miles

so.. whatever "x" is, we know 1125 + x = y
and whatever the alcohol concentration yield may be, we know
(1125)(0.9) = 0.75y
(1125)(0.9) = 0.75y <--- solve for "y", that's how much the final amount of milliliters will be
how much pure water was added? subtract 1125 from that, or y - 1125
Answer:
The measure of smaller angle = 45°
Step-by-step explanation:
Finding the unknown angle
Ratio of the supplementary angles = 3 :1
The angles are 3x , x
Supplementary angles add up to 180°
3x + x = 180
4x = 180
x = 180 ÷ 4
x = 45°
3x = 3*45 = 135°