Answer:
the answer should be 8.9
you square 12 and square the 8 and subtract them by each other
-11 = a + 7 Given
-7 -7 Subtract 7 on each side to cancel out +7 and isolate variable
-18 = a Answer
Prove.
-11 = -18 + 7 Plug in variable value
-11 = -11
True.
Answer:
Yes.
Step-by-step explanation:
Yes. Because opposite angles are congruent.
Given equation is y=2x+7 and 
Let's simplify the 2nd equation
before we can start graph so that calculation will be easy

multiply both sides by 2 to cancel out fractions

y=2x+7
which is exactly same as the first equatoin so graph of both will be exactly same and solution will be infinitely many solutions.
y=2x+7 has y-intercept 7 so first point will be (0,7). Slope is 2 so rise 2 unit up then 1 right and graph the new point.
The least common denomonator is 60