We know that 16 cups are in 1 gallon
We also know that 10 servings = 2 cups
Now that means 80 servings = 1 gallon
That means we need 320 / 80=4
It is A 4 gallons
Hope this helps
You would do
51-5= 46
then you would divide
46/2= 23
so Susan is
23+5=28
Susan is 28 years old and her sister is 23
28+23=51
Yes the first one is the correct answer in this form of a graph