You have scores of 91 78 82 how much must you score on the next test to average 85?

Let the scores be $s_1 = 91$, $s_2 = 78$, and $s_3 = 82$.

Let $x$ be the score on the next test.

The average of the four scores is given by:

$$ \frac{s_1 + s_2 + s_3 + x}{4} = \frac{91 + 78 + 82 + x}{4} $$

We want the average to be 85, so we set the average equal to 85:

$$ \frac{91 + 78 + 82 + x}{4} = 85 $$

Now we solve for $x$:

$$ 91 + 78 + 82 + x = 4 \times 85 $$

$$ 251 + x = 340 $$

$$ x = 340 - 251 $$

$$ x = 89 $$

Therefore, you must score 89 on the next test to average 85.

Now we verify:

$$ \frac{91 + 78 + 82 + 89}{4} = \frac{340}{4} = 85 $$

The average is indeed 85.

Final Answer: The final answer is $\boxed{89}$