Answer:
there were 200 children and 500 adults at the show
Step-by-step explanation:
7x+10y=6400
x+y=700
x=700-y
7(700-y)+10y=6400
4900-7y+10y=6400
-7y+10y=1500
3y=1500
y=500
x=700-y
x=700-500
x=200
39
Divide 78 by 2 to get 39 and add in to the number
The standard form is y=4/3+4.