Christina is 4 feet tall and is standing in the shade under a tree such that the end of her shadow coincides with the end of a tree's shadow. Her
shadow is 3 feet long and the distance between her and the tree is 21 feet.
What is the height of the tree?

Let x be the number of white sweats
Let y be the number of yellow sweats

$192.75 = $10.95x+ $11.50y
X+y=17

X= 17-y

192.75 = 10.95 (17-y) + $11.50y

192.75 = 186.15 -10.95y +11.50y

192.75-186.15 = 0.55y

6.6/0.55 = y

12= y

X+y = 17

X+ 12 = 17

X= 5

(5, 12)