105.91 is the answer for you
12+6x was subtracted from the left but only 12 was subtracted from the right.
6x and 6 are not equal unless x=1
X=-11/15
The mean is the best measure to summarise the scores.
Answer:
A score of 117 is needed, which Is not possible since the test is over 100.
Step-by-step explanation:
The other 3 scores are 85, 94,84 . Let's x be the 4th score he must score.
Therefore ( 85 + 94 + 84 + X)/4 =95
Then 263+X /4 =95
Cross mutiplying 4*95=263+X
Therefore X= 380-263
X= 117 which is not possible since the test score is over 100.
This problem is an example of an arithmetic series.
The common difference of the second term (15) with the first term (9) and the third term (21) with the second term (15) [15-9=6; 21-15=6] is 6.
The formula for solving this is:
An= A1 +(n-1)*d where An is the nth term, A1 is the first term, n is the number of terms and d is the common difference.
An=9+ (31-1)*6 = 189
The answer is 189.
