Simplify the expression by combining like terms 18z +9z

Anumber cube is rolled and a coin is tossed. the number cube and the coin are fair. what is the probability that the number rolled is less than 4 and the coin toss is tails?

An automated water dispenser fills packets with one liter of water on average, with a standard deviation of 5 milliliter. the manual says that after a year of operation the dispenser should be tested to see if it needs recalibration. a year later a number of filled packets are set aside and measured separately. it is found that the average packet now contains about 0.995 liters. does the dispenser need calibration? explain your answer.

The size of a certain cell is 2.5*10^-9m. another cell is 1.5*10^3 times larger. how large is the larger cell in scientific notation?