Which of the following contains a variable?

a. the mass is 95 kilograms.

b. sally ran twice as fast as sue.

c. they drove 49 miles per hour.

d. she has 5 sisters.

Initially 100 milligrams of a radioactive substance was present. after 6 hours the mass had decreased by 4%. if the rate of decay is proportional to the amount of the substance present at time t, find the amount remaining after 24 hours. (round your answer to one decimal place.)

Look at attachment. has all info needed. need

Sketch the region enclosed by the given curves. decide whether to integrate with respect to x or y. draw a typical approximating rectangle and label its height and width. y= 5x, y=7x^2then find the area s of the region.