21 cans of dog food.
She gives 21/3, or 7 cans to her neighbor.
She now has 21 - 7, or 14 cans for her puppy.
Her puppy eats 4/7 cans a day.

Jasmine has
8 days supply of dog food for her puppy.
Answer:
Step-by-step explanation:
First, look at y = log x. The domain is (0, infinity). The graph never touches the vertical axis, but is always to the right of it. A real zero occurs at x = 1, as log 1 = 0 => (1, 0). This point is also the x-intercept of y = log x.
Then look at y = log to the base 4 of x. The domain is (0, infinity). The graph never touches the vertical axis, but is always to the right of it. Again, a real zero occurs at x = 1, as log to the base 4 of 1 = 0 => (1, 0).
Finally, look at y=log to the base 4 of (x-2). The graph is the same as that of y = log to the base 4 of x, EXCEPT that the whole graph is translated 2 units to the right. Thus, the graph crosses the x-axis at (3, 0), which is also the x-intercept.
Ok so we'll go ahead and solve for y first - we just need to get it alone on one side of the equal sign
Step 1: subtract 2x from each side
2x - 7y - 2x = 19 - 2x
This cancels out the 2x on the left, giving us
-7y = 19 - 2x
Step 2: divide both sides by -7
=
+ 
This gives us
y = -19/7 + 2x/7
That should be your answer for the first question. Now solving the next parts are easy. All you need to do is plug in x.
When x = -3
y = -19/7 + 2x/7
y = -19/7 + 2(-3)/7
y = -19/7 - 6/7
y = -25/7
When x = 0
y = -19/7 + 2x/7
y = -19/7 + 2(0)/7
y = -19/7
When x = 3
y = -19/7 + 2x/7
y = -19/7 + 2(3)/7
y = -19/7 + 6/7
y = -13/7
Hope that helps! Feel free to ask if I can help with anything else :)