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.
Yes what is the four question
I don’t know about a ratio table but she makes 18 dollars per hour
<h3>Given</h3>
... r + 7 = 9
<h3>Find</h3>
... r
<h3>Solution</h3>
Subtract 7 from both sides of the equation.
... r + 7 - 7 = 9 - 7
... r = 2 . . . . . . simplify
Expressed as a solution set, this may look like ...
... r ∈ {2}
_____
You probably had no trouble solving this in 2nd grade when it was shown to you in the form ...
__ + 7 = 9
Answer:
1.- He received 388 dollars in exchange.
2.-(100 x 4) - (7.00 + 5.00)
= 400 - 12
= 488
3.- I buy 15 basketballs.
And I buy 6 soccer balls.
4.- (135 ÷ 9) (48 ÷ 8)
= 15, 6
Step-by-step explanation:
I hope I have helped you can you put that this is the smartest answer please?