Let 
be the 20 marks of the boys, and 
be the 10 marks of the girls.
We know that the global mean was 70, meaning that
Multiplying both sides by 30 we deduce that the sum of the scores of the whole classroom is
By the same logic, we work with the marks of the boys alone: we know the average:
And we deduce the sum of the marks for the boys:
Which implies that the sum of the marks of the girls is 
And finally, the mean for the girls alone is
X must be 4.
I uploaded the photo as an answer
Answer:
The answer to this equation will be 2 for x
Step-by-step explanation:
Hope this Helped
Answer:
Step-by-step explanation:
The rate of change of the function f(x) from point 
to point 
can be calculated using formula
Given
From the graph of the function
So, the rate of change is
The answer is (5,3). You need to equal both sides out. So 5x-22=4x-17. That will give you x=5. After that you substitute 5 for x in one or both of the equations and get that y=3. Hope this helps!
