Maggie wants to have an average of 92 in math class for 7th grade. She earned a 90 for the first trimester and a 87 for the second trimester. What grade does she need to earn for the third trimester in order to have a 92 average for the year?

So, basically we need to find the mean of all the scores

The mean would be the sum of all scores divided by the number of scores

So we have the information that one score is 90, second score is 87 and she what's to have a total score of 92

Given this information, our equation would be 90+87+x divided by 3 = 92

Where x is the unknown value and the score for the third trimester. We divide by three because that's the amount of scores we are given

With our equation, we add 90 and 87 together,which gives us 177

So, now we have 177+x divided by 3=92

We move three to the other side and it by multiply 92
92*3= 276

177+x= 276

We move 177 to the other side as a negative number to get the value of x
276-177 is equal to 99

So, Maggie must score 99 on her next test to get an average of 92