Answer:
none of them
Step-by-step explanation:
The Solution.
Representing the problem in a diagram, we have
By formula,

In this case,

Substituting these values in the formula above, we get

Clearing the bracket, we get



Dividing both sides by 2, we get

Therefore, the correct answer is option C.
Answer:
So a triangle has to be 180° overall And that is an equilateral triangle therefore every angle is equal so every angle inside is 60° so ?=60° another way you can find this out is a straight line is equal to 180° and since you have the external angle which equals 120° you do 180°-120° and get 60° and the 180°-60°-60°=60° and that’s your mystery angle. I hope that’s not too confusing.
Answer:
n does not have a defined value, but it has only one value, it is only possible to determined it in an equality let's say that 5n+21=26 there n =1
but we don't know the value
so it stays as 5n+21