let 'x' be the number of Php5 tickets (adult)
'y' be the number of Php2 tickets (children)
x + y = 1,750 ----equation 1
5x + 2y = 7,100 ----equation 2
multiply equation 1 with 2
[x + y = 1,750] x2
2x + 2y = 3,500 ----equation 1'
subtract equation 1' from equation 2
5x + 2y = 7,100
- 2x + 2y = 3,500
3x + 0y = 3,600
3x = 3,600
x = 1,200 tickets
substitute x=1200 to equation 1
x + y = 1,750
1200 + y = 1,750
y = 1,750 - 1200
y = 550 tickets
