Exercise 14 Page 742

The mean is often referred to as the average. It is used to describe the middle point in a set of data that does not have an outlier. To find the mean, we divide the sum of the values by the total number of values. Mean: Sum of the values/Total number of values We can write an expression for the sum of the grades and simplify it.

31.7 + 42.8 + 26.4+x

AddTerms

Add terms

100.9+x

We know that the total number of values is 4. Therefore, to find an expression for the mean we must divide the obtained expression by 4. Mean: 100.9+x/4 Finally, since we want the average — or mean — to be 35, the above expression must equal 35. Let's write an equation for this and then solve for x.

100.9+x/4=140

MultEqn

LHS * 4=RHS* 4

100.9+x=140

SubEqn

LHS-100.9=RHS-100.9

x=39.1