Atrain travels at a constant rate of 30 miles per hour. how long will it take the train to travel 100 miles

Achemist has 200 ml of a 10% sucrose solution. she adds x ml of a 40% sucrose solution. the percent concentration, y, of the final mixture is given by the rational function: the chemist needs the concentration of the final mixture to be 30%. how many milliliters of the 40% solution should she add to the 10% solution to get this concentration?

Iknow the answer but the calculator doesn't seem to give the right one

If the alternate hypothesis of an experiment is “the true mean height of the giraffes is more than 15 feet” what is the null hypothesis?