Answer:
<u><em>You will need to purchase 16 more gallons that cost $2.29 each for your final amount to be $36.64</em></u>
Step-by-step explanation:
You need to find how many miles you can get per gallon to use 160 miles on 5 gallons.
=
. Meaning your unit rate for this would be 32 miles for 1 gallon
You then need to find out how many gallons you will need if you're going to 640 miles and get 32 miles per gallon.
= 20
Meaning you will need 20 gallons.
Now since you already know how many gallon you have which is 4. Then you know how much you need, 20 - 4 = <u>16</u>
Then since they will be $2.29 each, multiply 2.29 by 16 to get <u>$36.64</u>
Meaning you will need to <u><em>16 gallons costing 2.29 each</em></u> and you will spend <u><em>$36.64 dollars on the trip</em></u>
Factorise to (5z-1)(z-4) = 0
then put 5z-1 = 0 so 5z = 1 z = 1/5
z-4=0 z = 4
z = 1/5 and 4