Salma has scored $80,88,87,58$, and 69 on her previous five tests. What score does she need on her next test so that her average (mean) is $78 ?$

Step 1 ：First, we need to calculate the total score Salma has so far. This can be done by adding all her previous scores together. So, \(80 + 88 + 87 + 58 + 69 = 382\).

Step 2 ：Next, we need to find out what total score Salma needs to have an average of 78 after six tests. This can be done by multiplying the desired average by the number of tests. So, \(78 * 6 = 468\).

Step 3 ：Finally, we need to find out what score Salma needs on her next test. This can be done by subtracting the total score she has so far from the needed total score. So, \(468 - 382 = 86\).

Step 4 ：Final Answer: Salma needs to score \(\boxed{86}\) on her next test to have an average of 78 after six tests.