The average of marks obtained by S1 and S2 is 35 more than the average of marks obtained by S2 and S3 . If the marks obtained by S3 is 75, then what are the marks obtained by S1?

Correct option is D

Given:
Average of marks obtained by S1 and S2 = Average of marks obtained by S2 and S3 + 35
Marks obtained by S3 = 75
Formula Used:
Average = (Sum of values) / (Number of values)
Solution:

Let the marks obtained by S1 be x and by S2 be y.
According to the question,
(S1 + S2)/2 = (S2 + S3)/2 + 35
Substitute the value of S3 = 75:
(x + y)/2 = (y + 75)/2 + 35
Simplify the equation:
x + y = y + 75 + 70
x + y = y + 145
Therefore, x = 145