Assuming Total Salary is 5 units.
Television Set + Remainder = Total Salary
Television Set + Remainder = 5 units
Then he also bought a DVD player. And 2/5 of Total Salary was left unspent after all his purchases. Since Total Salary is 5 units, then the Unspent Amount is 2 units.
Television Set + (DVD Player + Unspent Amount) = 5 units
Television set + (DVD player + 2 units) = 5 units
However, it also says after spending on the television set, he spent 1/3 of the Remainder on DVD player.
Remainder = DVD Player + Unspent Amount
Remainder = DVD Player (1/3) + Unspent Amount (2/3)
But since Unspent Amount is equivalent of 2 units, then this means that DVD player is equivalent of 1 unit.
Television + DVD player + 2 units = 5 units
$1280 + 1 unit + 2 units = 5 units
1 unit = $1280/2 = $640
Total Salary = 5 units = 5 x $640 = $3200