Answer:
See below
Step-by-step explanation:
The three angles inside of the triangle sum to 180
11x + 4 + 3x + 78 = 180
14x +82 =180
x = 7
then B = 11x + 4 = 11(7) + 4 = 81 degrees
C = 3x = 21 degrees
We have been given the steps to solve the equation as
Step 1: 2x = 18
Step 2: x = 18 − 2
Step 3: x = 16
There is an error in step 2.
We have 
x is in multiplication with 2. So in order to get rid of 2 from the left hand side, we perform opposite operation of multiplication i.e. division.
So we must divide both sides by 2.
Therefore, A is the correct option.
A) She did not divide 18 by 2.
Answer:
(i) The length of AC is 32 units, (ii) The length of BC is 51 units.
Step-by-step explanation:
(i) Let suppose that AB and BC are collinear to each other, that is, that both segments are contained in the same line. Algebraically, it can be translated into this identity:

If we know that
and
, then:


The length of AC is 32 units.
(ii) Let suppose that AB and AC are collinear to each other, that is, that both segments are contained in the same line. Algebraically, it can be translated into this identity:


If we know that
and
, then:


The length of BC is 51 units.