b = number of tickets sold before
a = number of tickets sold after
cost of a ticket = number of tickets times cost per ticket
before cost = 39.95b
after cost = 54.95a
total cost = 925000
39.95b + 54.95a = 925000
total number tickets = 20000
b + a = 20000
we have
39.95b + 54.95a = 925000
b + a = 20000
multiply second equation by -39.95 and add to first equation
39.95b + 54.95a = 925000
-39.95b-39.95a = -799000 +
0b+15a = 126000
15a = 126000
divide bot sides by 15
a = 8400
sub back
b + a = 20000
b+8400 = 20000
minus 8400 both sides
b = 11600
11,600 tickets sold before
8400 tickets sold after