The way we can find out the unit rate (also known as the <em><u>SLOPE</u></em>) is by using the table as coordinates!
The slope formula is 
With the table, the TIME column can be "x"
The DISTANCE column can be "y"
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As coordinates, it would look like...
(0,0)
(20, 25)
(30, 37.5) and so on!
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All we need to do now is use 2 of these coordinates and plug them into the slope formula in their correct places to find the unit rate!
Example:
solve!
= 12.5/10 ⇒ 1.25 ( or 5/4 in fraction form)
20% = 0.20
1254 x 0.20 = 250.80
so he has $250.80 deducted every month
2(z-10)=-4
2z-20=-4
2z=16
z=8
You need to divide 179.10 by 6