Answer: $90
Explanation:
Let the original cost be represented by x
From the question, it was given that the cost of headphones at 40% discount is $36
Thus, 40% discount = $36
100% = x
Then, convert to decimal
40% = 40/100 = 0.4
100% = 100/100 = 1
Therefore, 0.4 = $36
1 = $x
0.4x = $36
Divide both sides by 0.4
x = $36/0.4
x= $90
Original cost of the headphone was $90.
I hope this helps.