Which expression represents”9 less than the product of 5 and a number n”?

9 less means subtract

the product of 5 and the number n mea multiply 5 and n

D. 5n-9

5n-9 because less than means subtract and product means multiply

0.02

step-by-step explanation:

time of 9 192 631 770 periods of the radiation corresponding to the transition between the 2 hyperfine levels of the ground state of the caesium 133 atom at 0 k (but other seconds are sometimes used in astronomy)