Find the value of x (please help )

Ricardo ran the 400 meter race 3 times his fastest time was 54.3 seconds his slowest time was 56.1 seconds if his average time was 55.0 seconds what was his time for the third race

There are 45 questions on your math exam. you answered 810 of them correctly. how many questions did you answer correctly?

240 seventh graders and two-thirds of the students participate in after-school activities how many students participate in after-school activities