Answer:
$1,760
Explanation:
Let his salary be x.
He spent 1/5 of his salary, or x/5, and 1/8 of his salary, or x/8.
His salary was x. He spent x/5 and x/8, so we subtract those two amounts from his salary.
x - x/5 - x/8 is the amount he still has. He still has $1188. We equate the two and have an equation.
x - x/5 - x/8 = 1188
x/1 - x/5 - x/8 = 1188
We need to combine the three fractions on the left side, so we need to use a common denominator. The least common multiple of 1, 5, and 8 is 40, so 40 is the LCD.
40x/40 - 8x/40 - 5x/40 = 1188
27x/40 = 1188
Multiply both sides by 40.
27x = 47,520
Divide both sides by 27.
x = 1,760
Answer: His monthly salary is $1,760.
Check:
1/5 of his salary is 1760/5 = 352
1/8 of his salary is 1760/8 = 220
Now we subtract 352 and 220 from 1760.
1760 - 352 - 220 = 1188 which is what the problem stated.
Our answer, $1760, is correct.