Answer:
x = 18
Step-by-step explanation:
To solve this problem, we can use the exterior angle theorem, which means the measure of an exterior angle is the sum of its remote interior angles. In this case, this would mean:
x + 72 = 5x
Since this gives us an equation, we can just solve for x:
x + 72 = 5x
72 = 4x
x = 18
Answer
Elena must have substracted 1/2x from both sides of the equation.
Lin must have multiplied both sides of the equation by 2
Explanation
The equation given is

For Elena to have arrived at

Then Elena must have substracted 1/2x from both sides of the equation.
That is;

For Lin to have arrived at

It shows Lin must have multiplied both sides of the equation by 2
That is;
You can simply collect terms, subtract the constant and divide by the x-coefficient. It is generally considered easier to do those steps if you eliminate fractions first (multiply by 12).
Multiply by 12
... 4(x -1) +3(x +5) = 6
... 4x -4 +3x +15 = 6 . . . . . eliminate parentheses
... 7x +11 = 6 . . . . . . . . . . . .collect terms
... 7x = -5 . . . . . . . . . . . . . . subtract the constant 11
... x = -5/7 . . . . . . . . . . . . . divide by the x-coefficient
_ _ _ _ _ _ _
Here it is the other way.
... x(1/3 +1/4) +(-1/3 +5/4) = 1/2
... (7/12)x + 11/12 = 1/2 . . add the fractions to finish collecting terms
... x + 11/7 = 6/7 . . . . . . . multiply by 12/7
... x = -5/7 . . . . . . . . . . . subtract 11/7
At the third step here, you could subtract 11/12 before doing the multiply. You get the same answer, but you have to do the extra conversion of 1/2=6/12.
7v = 2v - 20
First, subtract 2v from both sides. / Your problem should look like: 7v - 2v = -20
Second, simplify 7v - 2v to 5v. / Your problem should look like: 5v = -20
Third, divide both sides by 5. / Your problem should look like: v =
Fourth, simplify

to 4. / Your problem should look like: v = -4
Answer:
v = -4
The answer is true since the triangles are similar on all lengths and angles