The admission fee at a small fair is $1.00 for children and $4.00 for adults. On a certain day, 1800 people enter the fair and $4800 is collected. How many children and how many adults attended?

Lets x = # of children attended the fair

y = # of adults attended the fair

x + y = 1800 so x = 1800 - y

x + 4y = 4800 so x = 4800 - 4y

So now you have

1800 - y = 4800 - 4y

4y - y = 4800 - 1800

3y = 3000

y = 1000

x = 1800 - 1000 = 800

answer:

children: 800 and adults: 1000

double check:

800 + 1000 = 1800 (1800 people enter the fair)

x + 4y = 4800

800 + 4 (1000) = 4800

800 + 4000 + 4800

4800 = 4800 ($4800 is collected)