Which expression has the greatest value |-21|, |14|, |30|, |-45|

|-45|

Step-by-step explanation:

In mathematics, the absolute value of a real number is the numeric value of the number, regardless the sign, either this is positive or negative.

The absolute value function can be definied as:

|a|=a si a ≥0 |a|=-a si a <0

Using this definition, we have:

|-21| = - (-21) = 21

|14| = 14

|30| = 30

|-45| = - (-45) = 45

Therefore, the expression |-45| has the greatest value.