A professor grades students on three tests, four quizzes, and a final examination. Each test counts as two quizzes and the final examination counts as two tests. Sara has test scores of 74, 80, and 83. Sara's quiz scores are 88, 77, 79, and 89. Her final examination score is 74. Use the weighted mean formula to find Sara's average for the course. (Round your answer to one decimal place.)

Step-by-step explanation:

We assume that the data is this one:

x: 50, 55, 50, 79, 44, 37, 70, 45, 49

y: 152, 53, 22, 35, 38, 166, 13, 185, 25

Find the least-squares line appropriate for this data.  

For this case we need to calculate the slope with the following formula:

Where:

So we can find the sums like this:

With these we can find the sums:

And the slope would be:

Nowe we can find the means for x and y like this:

And we can find the intercept using this:

So the line would be given by: