now, bear in mind that all these ones are lines, and to graph a line all you need is two points, so let's pick a couple of random values for say "x" and let's see what we get for "y" and that's our x,y point.
3)
![9x+4y=-16\implies \stackrel{\textit{using x = 0}~\hfill }{9(0)+4y=-16}\implies 4y=-16 \\\\\\ y=\cfrac{-16}{4}\implies y=-4~\hspace{10em}(0~~,~~-4) \\\\[-0.35em] ~\dotfill\\\\ 9x+4y=-16\implies \stackrel{\textit{using x = -4}~\hfill }{9(-4)+4y=-16}\implies -36+4y=-16 \\\\\\ 4y=20\implies y = \cfrac{20}{4}\implies y = 5~\hspace{10em}(-4~~,~~5)](https://tex.z-dn.net/?f=9x%2B4y%3D-16%5Cimplies%20%5Cstackrel%7B%5Ctextit%7Busing%20x%20%3D%200%7D~%5Chfill%20%7D%7B9%280%29%2B4y%3D-16%7D%5Cimplies%204y%3D-16%20%5C%5C%5C%5C%5C%5C%20y%3D%5Ccfrac%7B-16%7D%7B4%7D%5Cimplies%20y%3D-4~%5Chspace%7B10em%7D%280~~%2C~~-4%29%20%5C%5C%5C%5C%5B-0.35em%5D%20~%5Cdotfill%5C%5C%5C%5C%209x%2B4y%3D-16%5Cimplies%20%5Cstackrel%7B%5Ctextit%7Busing%20x%20%3D%20-4%7D~%5Chfill%20%7D%7B9%28-4%29%2B4y%3D-16%7D%5Cimplies%20-36%2B4y%3D-16%20%5C%5C%5C%5C%5C%5C%204y%3D20%5Cimplies%20y%20%3D%20%5Ccfrac%7B20%7D%7B4%7D%5Cimplies%20y%20%3D%205~%5Chspace%7B10em%7D%28-4~~%2C~~5%29)
check the red line in the picture below.
4)

check the blue line in the picture below.
Hi!
We know the amount needed to make 8 pancakes. Dan wants to make 12 pancakes. 12/8 = 1,5, that's the ratio, we need to multiply each ingredient with 1.5 and we will get the amount needed to make 12 pancakes.
240 * 1,5 = 360 g of plain flour
2 * 1,5 = 3 eggs
600 * 1,5 = 900 ml of milk
Hope this helps!
It seems like there's a typo? The x and y rows are identical
Assuming there is no typo, then the input and the output are the same. Meaning that whatever you plug in, is what comes out. If the output is 40, then the input must be 40.
So the answer is 40 (assuming there are no typos made by your textbook or teacher)