Energy Efficiency Calculations

A car uses 100 J of gasoline. 83 J are turned into mechanical energy. How much should be turned into heat?

What does this equation mean? \(\frac{useful\ output}{input}\ \times\ 100\%\) 

A TV uses 200 J of electricity and transforms it into 125 J of sound and light and 75 J of heat. How efficient is it?

My dog likes to run and bark. If he eats 1000 J of food, and transforms that into 700 J of kinetic energy, 100 J of sound, and 200 J of heat, what is his efficiency?

What is the efficiency of the machine if the input is 263 J and the output is 142 J?

Total energy = 200J
Useful energy = 20J

Workout the efficiency of this lightbulb.
$$efficiency\ =\ \frac{useful\ enegy}{total\ energy\ in}\ \times100$$  

Total energy = 350J
Useful energy = 70J

Workout the efficiency of this iphoneX.
$$efficiency\ =\ \frac{useful\ energy}{total\ energy\ in}\ \times100\%$$  

Total energy = 34000J
Useful energy = 340J

Workout the efficiency of this vintage VW Beetle.
$$efficiency\ =\ \frac{useful\ energy}{total\ energy\ in}\ \times100\%$$  

What is the formula for calculating energy efficiency?

A light bulb uses 60 J of electrical energy and emits 15 J of light energy. What is its efficiency?