Wright 1.56 x 10^4 standard notation?

Maria walks a round trip of 0.75 mile to school every day.how many miles will she walk in 4.5 days

The weight of a radioactive isotope was 96 grams at the start of an experiment. after one hour, the weight of the isotope was half of its initial weight. after two hours, the weight of the isotope was half of its weight the previous hour. if this pattern continues, which of the following graphs represents the weight of the radioactive isotope over time? a. graph w b. graph x c. graph y d. graph z

Using only the digits 5, 6, 7, 8, how many different three digit numbers can be formed if no digit is repeated in a number?