This question is a little tricky. Carla had a bill of $15, which we will add to the cost of Rob's lunch. They left a 20% tip on the TOTAL cost of both their lunches, which should equal $6. 20% is equivalent to 0.2. So, the equation is 6=0.2(x+15). In other words, 20% of the sum of Carla and Rob's lunches is 6 dollars.
Answer: 6=0.2(x+15)
Answer:
a) For this case we can use the definition of weighted average given by:

And if we replace the values given we have:

b) 
c) 
Step-by-step explanation:
Assuming the following question: "One sample has a mean of M=8 and a second sample has a mean of M=16 . The two samples are combined into a single set of scores.
a) What is the mean for the combined set if both of the original samples have n=4 scores
"
For this case we can use the definition of weighted average given by:

And if we replace the values given we have:

b) what is the mean for the combined set if the first sample has n=3 and the second sample has n=5
Using the definition we have:

c) what is the mean for the combined set if the first sample has n=5 and the second sample has n=3
Using the definition we have:

Answer:
Membership decreased by an average of 6,600 people per year from Year 3 to Year 5
Step-by-step explanation:
The average rate of change from Year 3 to Year 5 will be given by the slope of the line joining the points;
(3, 96.8) and (5, 83.6)
The slope of a line given two points is calculated as;
( change in y)/( change in x)
In this case y is the number of members for a given year x.
average rate of change = (83.6-96.8)/(5-3)
= -6.6
Since the number of members is given in thousands, we have;
-6,600
The negative sign implies a decrease in the number of members. Therefore, membership decreased by an average of 6,600 people per year from Year 3 to Year 5
It is D, because you have to get the denomenator"s equal so 9 times 4 is 36 and you take the numerator's and times by the other's denominator then subtract them to get 5/36