Answer:
<u>a= -4</u>
Step-by-step explanation:
subtract 4a from both sides
add 15 to both sides
divide both sides by -3
(order of operations)
A unit rate simply means how many of one type of units you get per 1 other type of unit.
Examples of that:

This is rate of fluid flow of some pump for example. It pumps 300 liters every second.
Other example:

This is example for speed. Somebody is moving at 50 kilometers per hour (every hour he travels 50 kilometers)
I think that’s the answer
Answer 1000
Might be wrong