Let's imagine that we turn the machine on 100 times. (this will make the percent conversion easier)
the chance that works in the morning is 50% of 100 so it will work 50 times.
the chance that it will then continue for the rest of the day is 15% so 15%*50 (the number of times it worked), which is 7.5 times.
our times actually represented percent, so the answer is : 7.5%!
Are there any answer choices?