Answer:
60
Explanation:
The number is represented as x.
81 is added to a number is
81 + x
39 less than three times the number
3x - 39
So
81 + x = 3x - 39
Solve for x.
81 + x = 3x - 39 Add 39 to each side so 39 cancels on the right.
81 + x + 39 = 3x - 39 + 39
81 + x + 39 = 3x
81 + 39 + x = 3x
120 + x = 3x Subtract x from each side.
120 + x - x = 3x - x
120 = 3x - x
120 = 2x Divide each side by 2
120/2 = 2x/2
120/2 = x
60 = x