Question 70412
OK You can work this problem using two unknowns:

Let x=number of adult tickets sold
And y=number of child tickets sold

Then as you say:

20x+8y=3200--------------Equation 1.

The other equation is:

x+y=220-----------------Equation 2.

(1)         20x+8y=3200
(2)           x+y=220

multiply equation (2) by 8

(1)         20x+8y=3200
(2a)         8x+8y=1760

subtract (2) from (1)

12x=1440  divide both sides by 12

x=120-----------------------number of adult tickets sold

Now substitute x=120 into (2)
120+y=220  subtract 120 from both sides

y=100-----------------------number of child tickets sold

CK
120*20+100*8=3200
2400+800=3200
3200=3200

You can also work this problem using one unknown:

Let x=number of adult tickets sold

Then 220-x=number of child tickets sold

Now we are told that cost of adult tickets sold plus cost of child tickets sold equals $3200.  So our equation to solve is:

20x+8(220-x)=3200  get rid of parens
20x+1760-8x=3200 subtract 1760 from both sides

12x=1440  divide both sides by 12

x=120--------------------------------number of adult tickets sold
22-x=220-120=100----------------------number of child tickets sold



Hope this helps----ptaylor