Answer: Niko needs 9 marshmallows and 6 graham crackers to make 3 s'mores.
Step-by-step explanation:
Let x be the number of marshmallows , y be the number of graham crackers and z be the number of s'mores.
Then according to given question
Niko uses 12 marshmallows and 8 graham crackers to make 4 s'mores
gives the equation 12x+8y=4z
If we divide whole equation by 4 , we get the quantity of x and y to make z such that
![\frac{1}{4}(12x+8y)=\frac{1}{4}(4z)\\\Rightarrow3x+2y=z](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B4%7D%2812x%2B8y%29%3D%5Cfrac%7B1%7D%7B4%7D%284z%29%5C%5C%5CRightarrow3x%2B2y%3Dz)
Now to make 3 s'mores, we need to multiply the equation by 3 such that
![3\times(3x+2y)=3\times\ z\\\Rightarrow\ 9x+6y=3z](https://tex.z-dn.net/?f=3%5Ctimes%283x%2B2y%29%3D3%5Ctimes%5C%20z%5C%5C%5CRightarrow%5C%209x%2B6y%3D3z)
Thus Niko needs 9 marshmallows and 6 graham crackers to make 3 s'mores.