a = adult
c = child
10a + 6c = 18,800
a + c = 2,000
In the second equation, subtract c from both sides.
a = 2000 - c
Put this into the first equation.
10(2000 - c) + 6c = 18800
Multiply everything in the parenthesis by 10.
20,000 - 10c + 6c = 18,800
Combine like terms.
20,000 - 4c = 18,800
Subtract 20,000 from both sides.
-4c = -1,200
Divide -4 on both sides.
c = 300
Put this into the second equation.
a + 300 = 2,000
Subtract 300 from both sides.
a = 1,700
Hope this helps!
