Answer: $2400
========================================================
Explanation:
x = Mason's salary in dollars for that month
x/6 = one-sixth of his salary
x/6+800 = total amount spent (the x/6 dollars and $800 combined)
In total, he spent half his salary. This means he spent x/2 dollars for the month overall.
Set the two items equal to one another. Solve for x.
x/6 + 800 = x/2
6(x/6 + 800) = 6*(x/2) ... see note at the bottom of the page
x+4800 = 3x
4800 = 3x-x
4800 = 2x
2x = 4800
x = 4800/2
x = 2400
His monthly salary is $2400
1/6 of this is (1/6)*2400 = 2400/6 = 400 dollars. Add on the $800 he also spent to get a total of 400+800 = 1200 dollars spent, which is exactly one half of the $2400. The answer is confirmed.
-------
Note: I multiplied both sides by 6 to clear out the fractions. The value 6 is the LCD in this case.
