Math
posted by Layla .
A math teacher drove by a playground that was full of boys and dogs.The teacher notice there were a total of 40 heads and 100 feet. Hom many boys and how many dogs were there?

Let x = boys and y = dogs
x + y = 40, then x = 40y
2x + 4y = 100
Substitute 40y for x in second equation and solve for y. Insert that value into the first equation and solve for x. Check by inserting both values into the second equation. 
10 dogs
30 kids 
24=2=+y=y765