Answer :
Number of economy seats are 181
What is linear equation?
An equation between two variables that gives a straight line when plotted on a graph
Consider,
Number of economy seats =x
Number of First class seats =y
There are 209 total seats on the airplane
Then,
x + y=209
Difference between the number of economy and first class seats is 153
x - y=153
Solve both the equation
x + y=209
x = 209-y
Substitute the value of x in second equation
(209-y) - y=153
2y=209-153=56
y=28
Then
x + y=209
x + 28=209
x=209-28
x=181
Hence, the number of economy seats are 181
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