At a police checkpoint for drunk drivers, some cars are stopped at random; many others are not stopped. The cars that are stopped may be considered a of all the cars that pass by the checkpoint.

sample

or spot check

Step-by-step explanation:

there are quite a number of different terms that can be used depending on the specific scientific field you are working in.

but "sample" should be the most common one for a random selection of a subset of the whole set.

phosphate, calcium ion, chloride ion, neon atom

step-by-step explanation:

$53.50

step-by-step explanation:

you have to subtract the amount of money chuck earned ($72.50) by the cost of the gas for the mower ($11.25) and the new string for the trimmer he bought ($7.75).

72.50-11.25=61.25

and then subtract $61.25 by the second thing he bought (the new string for the trimmer)

61.25-7.75=53.5

so in total it's $53.50 (53 dollars and 50 cents)