Answer:
6+f=21
Step-by-step explanation:
The sorting as been done below:
<h3>What is Unit?</h3>
A unit of measurement is a quantity used as a standard to expressed a physical quantity.
Volume: Millimeter , Kiloliter
Length: Yard, Quart
Weight/Mass: Centigram, Ounce.
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In a - 3 = 15, the value of a HAS to be 18.
In a - 3 is greater than or equal to 15, the value of a is any value that is 18 or higher.