How do you do this this question?

You take the average of the test scores including the final and make it greater than or equal to 80. The final counts as two tests. Let's say the final exam score is "x".



Then you solve for x the final exam grade to get a B in the class.
start by multiplying the 5 over to the other side and adding the exam grades.

238 + 2x ≥ 400

subtract 238 from both sides

2x ≥ 162

divide by 2

x ≥ 81

since the final counts as 2 tests they need to score at least an 81 to get an 80 average for the course.