We have to formulate a system of equations with the information given. Doing so, we have:
x= Evening flight passengers
y= Morning flight passengers
x= 2y - 6 Eqn(1)
x + y = 753 Eqn(2)
Then, we use the substitution method to solve for y:
(2y-6) + y = 753 (Substituting x=2y - 6 in the Eqn(2))
3y - 6 = 753 (Adding like terms)
3y = 753 + 6 (Adding 6 to both sides of the equation)
3y = 759 (Adding)
y = 759/3 (Dividing on both sides by 3)
y = 253 (Dividing)
We can see that the answer is 253 passengers.