X + 3 = 8
x = 8 - 3
x = 5 <=
The formula of the Simple Interest is:
I=PRT
P for Principle Amount ($1200)
R for Rate (5%=

= 0.05)
T for Time in years (4 years)
I = 1200 × 0.05 × 4
= $240
Add the interest to the principle amount to check the balance
$1200 + $240 = $1440
Complete question :
Mr. Nelson lost one of his students' test papers. He knows that the other 4 students scored as follows: 60, 62, 56, 57. He also knows that the average score is 59.2. What is the score on the missing paper?
Answer:
61
Step-by-step explanation:
Given the following :
Total number of students = 4 + 1 missing = 5
Score on the four avaliable papers = 60, 62, 56, 57
Average score of the 5 papers = 59.2
Score on missing paper :
Sum of each score / number of papers
Sum of each score = sum of available scores + missing score
Let missing score = m
(60 + 62 + 56 + 57 + m) = 235 + m
Recall:
Average = total sum / number of observations
Hence,
59.2 = (235 + m) / 5
59.2 × 5 = 235 + m
296 = 235 + m
m = 296 - 235
m = 61
Missing score = 61
8-15= -7
x= -7
I think this is correct..