The average of the numbers 52,87,k,103,48,(k+4),51 is 63. What is the value of k?

There are 7 observations in total: 52,87,k,103,48,k+4,51.
The formula for average is:

Average=
Number of observations
Sum of all observations
​

Given that the average is 63:

63=
7
52+87+k+103+48+(k+4)+51
​

Multiply both sides by 7:

63×7=441
Now sum up the constants in the numerator:

52+87+103+48+4+51=345
So the equation simplifies to:

345+2k=441
2k=441−345
2k=96
k=48