Solution:
Marks scored in English = 36
Marks scored in Civics = 44
Marks scored in Mathematics = 75
Marks scored in Science = x
No. of subjects = 4
Average marks = sum of marks / No. of subjects = 50 [Given]
(36+44+75+x)/4 = 50
155+x = 4×50
155+x = 200
x = 200-155
x = 45
Hence the value of x is 45.