Solution:
The square of the given equation can be completed as below:
Here we will make the terms on left hand side such that it gets the form of 
Hence the correct option is isolating the constant , -3.
Given
One month julia collected 8.4 gallons of rainwater.
she used 5.2 gallons of rainwater to water her garden
6.5 gallons of rainwater to water flowers
Find out how much was the supply of rainwater increased or decreased by the end of the month.
To proof
As given in the question
One month julia collected 8.4 gallons of rainwater
she used 5.2 gallons of rainwater to water her garden and 6.5 gallons of rainwater to water flowers
Total water she used in the month = 5.2 gallons + 6.5gallons
= 11.7 gallons
Let the supply of rainwater increased or decreased by the end of the month
be x .
Than the equation become in the form
x + 8.4 = 11.7
x = 3.3 gallons
Therefore the supply of rainwater increased or decreased by the end of the month is 3.3 gallons.
Hence proved
All you have to do is since one batch needs 1 1/3 cup of walnuts multiply 1 1/3 to 3 3/4 = 3 1/4 cups
