She would have to score at least a 97% on her next math test.
Mean = 88 + 94 + 82 + 89 + 97 = 450 450/5 = 90
You could have found this answer without using trial and error. If she wants to get a mean of 90 and she will have 5 tests, you can multiply these together. This equals 450. Now you need to find the minimum score she needs to get. Take 450 and subtract what the original 4 numbers equal, 353. This gives you 97. I hope that makes sense :)
(This is what I think) First, we minus 720 from her 1000. Now she has $280 left. 280 divided by 28 (the trainer cost) is 10. So, she can spend 10 hours with the personal trainer.
