Question 1063217
a+c = 350
c = 350-a
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5c+10a = 2000
5(350-a)+10a = 2000
1750-5a+10a = 2000
5a = 250
a = 50 
In order to make at least 2000 you need at least 50 adults and 300 children. Make your own additional combinations by increasing the number of adults and proportionally decreasing the number of children. Always calculate the total for each iteration:
adults...: 50*10 = 500
children: 300*5 = 1500
 total. . . . . . 2000
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adults. .: 60*10 600
children: 290*5 1450
 total . . . . .2050
:
etcetera