let 'x' be the number of persons w/ tickets @50 pesos
'y' be the number of persons w/ tickets @75 pesos
x+y = 863 ----equation 1
50x + 75y = 50,000 ----equation 2
from equation 1
x + y = 863
x = 863 - y ----equation 3
substitute equation 3 to equation 2
50(863-y) + 75y = 50,000
43,150 - 50y + 75y = 50,000
25y = 50,000 - 43,150
25y = 6,850
y = 274 persons
substitute to equation 1
x + y =863
x + 274 = 863
x = 863 - 274
x = 589 persons
therefore there are 274 persons who bought reserved seat tickets
