This is a geometric sequence that means there is a common ratio. That means there is a number you can multiply over and over to get the next term.
The first term is 27.
The second term is (1/3)(27)=9.
The third term is (1/3)(9)=3.
So the common ratio is 1/3.
That means you can keep multiplying by 1/3 to find the next term in the sequence.
The explicit form for a geometric sequence is where is the first term and is the common ratio.
We are given and .
So the explicit form for the given sequence is .
a triangle's full angle is 180 degrees so 180 - 156 = 24. 24/2=12