Question 1175290
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Hi
half as many adults as there are children. 
Let x = Adults & 2x Children
  5(2x)  + 7(145-3x) + 12x = 1040
         x = 1040 - 7*145
          x = 25, the number of Adults, 50 children & 70 Students {{{145-75}}}

$5*50 + $7*70 + $12*25 = $1040  checks
Wish You the Best in your Studies.
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