Question 1203161
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The total number of known moons around Saturn, Uranus, and Neptune is 43. 
The total number of moons around Saturn and Neptune is 9 more 
than the number of moons around Uranus. 
Saturn has 2 moons more than twice the number of moons around Neptune. 
Find the number of moons each planet has.
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Let N be the number of moons around Neptune.

Then the number of moons around Saturn is 2N+2, according to the problem.

The number of moons around Uranus is ((2N+2) + N - 9) = 3N-7.


Next, we have this equation for the total number of moons around the three planets

    N + (2N+2) + (3N-7) = 43.


Simplify and find N

    6N - 5 = 43

    6N = 43 + 5 = 48

     N = 48/6 = 8.


<U>ANSWER</U>.  There are 8 moons around Neptune;
         2*8+2 = 18 moons around Saturn, 
         and 3*8-7 = 17 moons around Uranus.


<U>CHECK</U>.  8 + 18 + 17 = 43 moons, total.   ! correct !
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Solved.