Answer
$$ 76.5 \le x \le 100$$
Work Step by Step
We know that she must average at least an 80 overall to earn a B in the course. We assume that the final is weighted the same as the other tests and use the equation for an average:
$$ 80 \lt \frac{80+90+82+75+x}{5} \lt 100 $$
where x is her score on the final
Then, follow PEMDAS. In other words, first address parentheses, and then resolve exponents. Next, simplify division and multiplication, and lastly address subtraction and addition. This gives:
$$ 76.5 \le x \le 100$$
