The law of cosines states that, if
is the angle between sides b and c,

So, plugging our values, we have

This is equal to

X + y = 40.....multiply by -4
4x + 6y = 180
-------------------
-4x - 4y = -160 (result of multiplying by -4)
4x + 6y = 180
------------------add
2y = 20
y = 20/2
y = 10 <===
x = 30
Answer:
The common ratio is 5 and the 5th term is 1250
Step-by-step explanation:
The common ratio is given by
r=U(2)/U (1)
=10/2
=5
The fifth term
U (n)=ar^n-1
U(5)=2(5)^5-1
=2×5^4
=2×625
=1250
The answer would be C) because there are 11 possibilities of who can line up first, and after the first person, 10 possibilities, then 9, and so on. So you would need to multiply 11x10x9x8x...x1.