Question 1019199
So we don't know how many months she was a member of the first gym and how many months, out of a year, she was a member of the 2nd gym. Let's find out, let's call the number of months of the membership at 75 x and the months at 50 y:
x+y = 12 subtract x from both sides:
y = 12-x we'll use this value for y next:
75x+50y = 775 Now substitute for y:
75x+50(12-x)= 775
75x+600-50x = 775
25x = 175
x = 7 She paid 75 during 7 months and 
12-7 = 5 months at 50
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Check:
7*75 = 525
5*50 = 250
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Total: 775 We have the correct answer