I used one of the most basic AP formulae to solve this question.
Treat the sequence as two arithmetic progressions (APs), as they have fixed differences involved.
For the 1st AP (increasing by 5), using the AP formula nth term = a+(n-1)d:
Peak term = 50+(m+1-1)(5) = 50+5m
The value of n here is m+1 because it is given that there are m integers after the first integer (pay attention to the keyword 'after' here)
For the 2nd AP (decreasing by 5), using the same AP formula again:
In this AP, the first term is 50+5m (the peak term), last term = 50 (given in the question) and the common difference = -2 (given in the question).
Let number of terms in this decreasing part be k. Thus,
50 = 50+5m+(k-1)(-2)
Simplifying, we get: k = (5m+2)/2
Since the total number of terms given in the AP = 36:
=> (m+1)+k-1 = 36
=> m+k = 36
Reasoning:Increasing AP has m+1 terms
Decreasing AP has k terms (including the peak term)
But the peak term gets counted twice, hence accounted for the same by -1 in the above equation.
Now, we have m+k = 36 and k = (5m+2)/2:
m + (5m+2)/2 = 36
Solving for the value of m, we get m = 10
Hence, the correct answer is
Option E - 10.
Hope this helps!