we have the numbers

we know that
The sum of a number and its additive inverse is 0
so

therefore
the number n is equal to 
the sum is equal to zero
the answer Part a) and Part b) in the attached figure
Answer:
it's a scalene triangle whose all sides are different
- 2(x + 7)
mutiply the bracket by -2
(-2)(x)= -2x
(-2)(7)= -14
Answer:
-2x-14