Laura has scored 75, 85, 81, 67, and 91 on her previous five tests. What score does she need on her next test so that her average (mean) is 77?

The answer is 63

You start off with 5 scores but you want to find the sixth score. And also you need the average to be 77. So you can set up the equation as (75+85+81+67+91+x) / 6=77. Then you can solve the equation. Start by multiplying both sides by 6 so the equation looks like 75+85+81+67+91+x=462. If you take all the numbers on the left and add them together you will get 399+x=462. Finally, you subtract the 399 from both sides. This will leave you with x=63. So the answer is 63.

63

Step-by-step explanation:

your equation should look like (75+85+81+67+91+x) : 6 = 77 first you multiply 6 to both sides. then you subtract all your previous numbers from 462 (the product of 6 and 77) and you should end up with 63