It depends on what you mean by 'electricity'. The problem is that 'electricity' is simply the name of an area of study, just like 'chemistry'. So you probably mean "How much 'energy' does a 60-W lamp use?" Energy is often measured in units called 'kilowatt hours', so to find how out much energy a 60-W lamp uses, you must first change 60 W into kilowatts, then multiply it by the number of hours for which the lamp is operating.