1.
2x+7=2x-7
2x-2x=-7-7
0=-14
Math error.
2.
3x+8=-2x+8
3x+2x=8-8
5x=0
x=0
3.
4(x+1)=4x+4
4x+4=4x+4
4x-4x=4-4
0=0
Correct

Why?
We can find the perimeter of any triangle adding the length of its sides. Since we are given 3 points, we need to calculate the length of the three sides of the triangle, and then add them to know the perimeter of the triangle.
Let be the points:
A(-3,-1)
B(-1,2)
C(6,1)
<h3>
- Distances</h3>
From A to B:

From A to C:

From B to C:

Now, calculating the perimeter, we have:

Have a nice day!
The four vertices of the new quadrilateral is the midpoints of the four sides. (5,3) and (5,-1) is ((5+5)/2,(3-1)/2)=(5,1). Midpoint between (-1,3) and (5,3)=(2,3). Midpoint between (-1,3) and (-1,-1) is (-1,1). Midpoint between (-1,-1) and (5,-1) is (2,-1). So the four vertices are (5,1), (2,3), (-1,1), and (2,-1). The resulting figure is a rhombus, centered at (2,1).
The answer is B hopefully this helped
49. $30.00 - $14.78 = $15.22 in change
50. 6.20 ft - 5.34 ft = .86 ft taller
51. 5.4 + 3.05(2) - 1.39 = 10.11 lbs