Answer:
maybe the arrows should start from zero, probably
I had this before and I think is was A.
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
Line perpendicular to a given line is = 1/m
To find m, use m =y2-y1/x2-x1 formula
m = (8-(-3))/(-7-4)
m = 11/-11,
m = -1
Use y= mx+c to find equation of line
Plug in a pair of values,
-3= -1(4)+ c
c= 1
Thus, equation is:
y = -x+1
Equation of line perpendicular to this line is:
y= x+1
Hope it helps :)
Pls mark it as Brainliest :)
Answer:
$5.61
Step-by-step explanation:
Since David only has $9.39 but he needs $15.00 for his purchase. So, you would subtract the $9.39 from the $15.00 to see how much more money David needs to make this purchase.
15.00 - 9.39
When you carry out this problem, it equals $5.61.
Therefore, David needs $5.61 to be able to complete his purchase
