Answer: There are 69 adults and 72 children went to the concert.
Step-by-step explanation:
Let x be the number of adults, and y be the number of children.
x + y = 141
3.5x + 2.5y = 421.5
x + y =141
x = 141 - y
3.5(141 - y) + 2.5y = 421.5
493.5 - 3.5y + 2.5y = 421.5
493.5 - y = 421.5
-y = -72
y = 72
x + y = 141
x + 72 = 141
x = 69
Answer: (13,-7)
Step-by-step explanation:
By using the formula 
is the coordinates of the midpoint.
For finding the midpoint X variable do:

For finding the midpoint Y variable do:
(you can either keep the parenthesis or take them out. Either way, the answer is the same.
Considering coordinate numbers follow the format: (x,y), you'll simply just substitute the numbers found above into their respective places.
x: 13
y: -7
(13,-7).
Answer:
A 5.25, B 5.75, C 10.25, D 25.8125
Step-by-step explanation: