Hey there!
Let's first define our goal. Our goal here is to be able to isolate the variable, n, and solve for it by moving everything to the other side. We see that we have two sides of the equation, and by using the property of equality which states that whatever you do to one side you do to the other and the expression remains equal, we can solve this equation.
It looks like the only thing we have on the left side with n is that 6 1/2. In order to get rid of it, we must subtract it from both sides, because the property of equality states you must do the inverse operation.
We have:
n = 12 - 6 1/2
n = 5 1/2
Hope this helps!
Answer:
and 
Step-by-step explanation:


and 
Answer:
A) The first 4 terms of the sequences are:
,
,
and
.
B) An explicit formula for this sequence can be written as: 
C) A recursive formula for this sequence can be written as:

Step-by-step explanation:
A) You can find the firs terms of this sequence simply selecting an odd integer and summing the consecutive 3 ones:
(a.1)




B) Observe the sequence of odd numbers 1, 3, 5, 7, 9, 11, 13(...).
You can express this sequence as:
(b.1)
If you merge the expression b.1 in a.1, you obtain the explicit formula of the sequence:
(a.1)
(b.2)
(b.3)
(b.s)
C) The recursive formula has to be written considering an initial term and an N term linked with the previous term. You can see an addition of 8 between a term and the next one. So you can express each term as an addition of 8 with the previous one. Therefore, if the first term is 16:
(c.s)
X=21
This is because both of those angles are equal, so you would divide 42 by 2 and get 21