Answer
Score needed = 85
Work Step by Step
Average = Sum of items $\div$ Number of items
Required average = 80
As the last test counts as 2 exams, let the score be "2x"; one "x" per test score.
= $ \frac{80 + 83 + 71 + 61 + 95 + x + x}{7} = 80$
= 390 + 2x = 560
2x = 560 - 390
2x = 170
x = 85
Score needed = 85
