Answer:-5
Step-by-step explanation:
You need to distribute on both sides so u get
9c-15=20-2c
Move variable to left side and change the sign
-9c+2c-15=20
Move constant to right side and change the sign
-9c+2c=20+15
Connect like terms
-7c=35
Divide
C=-5
Step-by-step explanation:
Because the length of ST is calculated using pythagorean theorem:

Where the square of the hypotenuse is equal to the sum of squares of the other two sides of a right triangle. In this case, the hypotenuse is ST and the other two sides are distances between S and T over the X and Y axis. Those are easily calculated:

Where x is the distance between S and T over X axis and Y distance over Y axis, sx and tx are X coordinates of S and T, sy and ty are Y coordinates of S and T.
Using that formula, you get that y = 17 and x = 8.
Back to the pythagorean theorem, if we put those number in the formula of the pythagorean theorem, we get something like this:

And finally, the correct answer is in fact 353.
The answer is going to be x=7
lines with undefined slope are vertical
equation are in form of x constant
through the points ( 3 , -4)
the line is x=3