Question

Plz help no guessing please

Answer 1

Well, if there is no restriction on how it is solved, the easiest way is to solve by guess and adjustment.

Assume everyone bought coach tickets, then
expense=15*220=3300
So there is (12930-3300)=9630 left over for them to switch to first class.
The
number employees who can switch to first class
 =9630/(1290-220)
=9630/1070
=9
So there are 9 first-class tickets and (15-9)=6 coach tickets.

Answer 2

Lets 
x = # of coach tickets and y = # of first class tickets

x + y = 15
220x + 1290y = 12930

x + y = 15 so x = 15 - y

substitute x = 15 - y into 220x + 1290y = 12930

220x + 1290y = 12930
220(15 - y) + 1290y = 12930
3300 - 220y + 1290y = 12930
1070y = 9630
y = 9

x = 15 - y
x = 15 - 9
x = 6

answer
6 coach tickets and 9 first class tickets