Solve for x and y:
3/x -1/y =13/10
1/x + 2/y =9/10

  (x, y) = (2, 5)

Step-by-step explanation:

I find it easier to solve equations like this by solving for x' = 1/x and y' = 1/y. The equations then become ...

  3x' -y' = 13/10

  x' +2y' = 9/10

Adding twice the first equation to the second, we get ...

  2(3x' -y') +(x' +2y') = 2(13/10) +(9/10)

  7x' = 35/10 . . . . . . simplify

  x' = 5/10 = 1/2 . . . . divide by 7

Using the first equation to find y', we have ...

  y' = 3x' -13/10 = 3(5/10) -13/10 = 2/10 = 1/5

So, the solution is ...

  x = 1/x' = 1/(1/2) = 2

  y = 1/y' = 1/(1/5) = 5

  (x, y) = (2, 5)

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The attached graph shows the original equations. There are two points of intersection of the curves, one at (0, 0). Of course, both equations are undefined at that point, so each graph will have a "hole" there.

the revenue of the fitness center, y, is the product of two factors: the number of members and the fee paid by each member. there are 320 members now, but number of members goes down by 10 for each $5 increase in fees, so if x is the number of $5 price increases then members is equal to (320 - 10x). since the fee is currently $45, and the fee increases by $5 for every price bump x, the fee is given by (45 + 5x). so, revenue y is given by y = (320 - 10x)(45 + 5x).