The sales tax is 2$ Hope this is the answer you're looking for.
Answer:
-- Proved

Step-by-step explanation:
Given


Required
Show that 
The volume is calculated as:

Open the brackets



Collect Like Terms


Divide through by 4


Solving further:
Expand the expression

Factorize:


Split:


First answer: 12
Second answer: 6
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How to get these answers
She uses 1/3 of a cup for 1 cake, so we have this ratio
1/3 cup : 1 cake
Multiply both sides by 3 and we end up with
1 cup : 3 cakes
Then multiply both sides by 4 to change "1 cup" to "4 cups" and we have
4 cups : 12 cakes which is the answer to the first part
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For part 2, we'll follow the same steps as before, but instead of multiplying both sides by 4, we do 2 instead because we're dealing with 2 cups of oil.
1/3 cup : 1 cake
3*(1/3 cup) : 3*(1 cake)
1 cup : 3 cakes
2*(1 cup) : 2*(3 cakes)
2 cups : 6 cakes which is the answer to the second part
Answer:
Step-by-step explanation:
multiply each side by 2
subtract 3 from each side
multiply each side by -1