Write the system of equation based on the problem "A total of 345 tickets that consists of adult tickets and students ticket were sold" could be written as: ∴ a + s = 345 <em>(first equation)</em> "<span>the number of student tickets sold was two times the number of adult tickets sold" could be written as: </span>∴ s = 2a <em>(second equation)</em> <span> Solve the system of equation Substitute 2a as s in the first equation a + s = 345 a + (2a) = 345 3a = 345 a = 345/3 a = 115