Answer: 90 Earth years.
Step-by-step explanation:
Analizing the information provided in the exercise, you need to find the Least Common Multiple (LCM) of the given numbers.
You can follow these steps:
1. You must descompose 6, 9, 15 and 18 into their prime factors:

2. Finally, you need to choose the commons and non commons with their greatest exponents and multiply them. Then you get:

Therefore, it will take 90 Earth years for them to all line up.
Answer:

Step-by-step explanation:
Solving trigonometric equations.
We are given a condition and we must find all angles who meet it in the provided interval. Our equation is

Solving for 5x:


The values for x will be


To find all the solutions, we'll give n values of 0, 1, 2,... until x stops belonging to the interval 
For n=0


For n=1


For n=2


For n=3


For n=4


For n=5 we would find values such as


which don't lie in the interval 
The whole set of results is

Answer:a
Step-by-step explanation:
Hey dhsidvxhejfbeifbshdjdbd