Answer:
15 J
Explanation:
There is a total of 100 J of energy being used which is then converted into sound energy, thermal energy, and friction. This means the total amount must equal 100 J.
1. Set up the equation
80 + x + 5 = 100
2. Simplify
x + 85 = 100
3. Solve for x by subtracting 85 from both sides
x = 15