Ticket rate for the science exhibition is 10 rupees for a child and 26 rupees for an adult. 740 rupees was got from 50 persons. How many children among them?

Let no. of children =X
number of adult = Y
 X + Y=50        ......equation (1)
X=50-Y
now
 10 X + 26 Y = 740     ........ equation (2)      
put  X=50-Y in equation (2)

10(50-Y)+ 26 Y=740
500-10Y + 26Y =740
16Y=740-500=240
16Y= 240
Y=
Y= 15
put in equation (1)
X+Y= 50
X+15= 50
X= 50-15=35
X=35
total no. of children = 35