Four students used the diagram shown to determine the value of x. Which student's reasoning is correct?

Suppose that in 2008 , 840,800 citizens died of a certain disease assuming the population of teh country is 399 miliion, what is the mortality rate in units of deaths per 100,000 people?

Find two numbers if their sum is 91 and the ratio is 6: 7?

The difference of three and the reciprocal of a number is equal to the quotient of 20 and the number. find the number.