The correct option is C 541 adults & 209 children
Let's say there are A adults and C children, then there are 4A plates for adults and 2C plates for children.
Lets form equations now
A + C = 750 .........(i)
4A + 2C = 2582 ........(ii)
Let's solve the above system of equations by elimination.
We can begin by multiplying equation (i) by 2.
Subtract that new equation from (ii)
4A + 2C = 2582
2A + 2C = 1500
______________
2A=10822
A = 541
Lets solve for C
Put A = 541 in first equation (i), we get
541 + C = 750
C = 750 - 541 = 209
Hence, option C is correct.