<PRE><B>Question 651748</B>
Cost of adult ticket= $15
Cost of child ticket= $10
Number of adults= x
Number of children= y
Total number of tickets= 140
 x+y = 140    .....(1)
Cost of x adult tickets= $15x
Cost of y child ticket=  $10y
15x + 10y= 1600 ...(2)
  x +  y = 140      
multiply this equation with 10 to make the coefficient of one variable same
 10x+ 10y = 1400  ....(3)
Subtract equation 2 and 3
15x-10x +10y-10y= 1600-1400
 5x = 200
  x = 200/5
  x = 40
Substitute the value of x in equation 1
 x+ y =140
 40 + y= 140 
 y= 140-40
 y= 100 </PRE>