Answer: The average was 9 years old find the average age of both groups is 10 years old.
Step-by-step explanation:
Formula foe average : 
Given : The first group of students consists of 10 and their average age was 13 years old.
i.e.
(1)
The next group consisted of 30 students and their average was 9 years old.
i.e.
(2)
Then from (1) and (2) , the sum of both groups (first group and next group )students = 130+270 =400
Combined students of both groups (first and next group )= 10+30=40
Now , the average of both groups =

Hence, the average was 9 years old find the average age of both groups is 10 years old.
C and E and F are all the correct answers
have you tried 42 because it's a 90 degree triangle and 30+18+42 equals 90
Answer:
To do this I am pretty sure your going to have to do some hard calculations.
<u><em>Lets go deeper</em></u>
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so because it is a rectangle every angle is a right angle according to the property of a rectangle.
A right angle is 90 degress
So 8x+18=90
90-18=72
8x=72
72/8=9
x=9
Feel free to do brainlest if correct
Answer:y=-3x+7
Step-by-step explanation:y+5=-3(x-4)
=>y+5=-3x+12
=>y=-3x+12-5
•°•y=-3x+7.