Answer:
1/2
Step-by-step explanation:
Please see attachment .
Cookies=x
brownies=y
.5x+.75y=100
.5x=100-.75y
x=200-1.5y
400-3y+.75y=100
-2.25y=-300
y=133.333
x=0
Begin by subtracting 1/8 from both sides to get

and get a common denominator of 8 on the right:

. Now simplify and cross-multiply: 39x = -16 andx = -16/39
Answer:
10 people,200 dollars. 20 people,400 dollars.100 people,2000 dollars.300 people,6000 dollars.