<PRE><B>Question 980207</B>
Hi there,
An aeroplane can carry 400 passengers in total
x + y = 400.......(1)
first class are allowed 30kg of luggage and economy class are allowed 20kg of luggage the maximum combined weight for the luggage of all passengers is 9200kg.
30x + 20y = 9200....(2)
...........  
x + y = 400.........(1)
30x + 20y = 9200....(2)
Multiply (1) by 30
30x + 30y = 12000....(1)
30x + 20y =  9200....(2)
Subtract (2) from (1)
.....10y = 2800
.......y = 280
Substitute y = 280
into (1)
x + y = 400
x + 280 = 400
x = 400 - 280
x = 120
120 First Class
280 Second Class
Hope this helps:-)</PRE>