Solution:
Given, total student = 240
Since, 10 student failed in every subject.
Hence, Remaining total = 230
Now, According to question,
a + b + c + d + e + f + g = 230 ...(i)
and b + c + d = 110 ...(ii)
and e + f + g = 60 ...(iii)
using equation (ii) and (iii) in equation (i), we get
⇒ a = 230 - (110 + 60) = 60