Ok so to find the mean of something, you add all the numbers and then divide by the amount of numbers. So we want to find what Martina has to score to get the mean of 73. We would show this by doing (75 + 77 + 74 + 92 + 61 + x ) / 6 = 73
We put an x to represent the upcoming test. So first we find the parenthesis which is (379 + x) /6 = 73. Now we want to get x alone so we multiply both sides by 6 so 379 + x = 438. Now we subtract 379 from both sides which is x = 59.
So Martin must score a 59 to get an average of 73
To check my answer do 75+77+74+92+61+59= 438 / 6 = 73
So it is correct.
Hope that helped! if you don't get it ask and i can try to re explain.
