A gallon of milk costs $1.99.A half-gallon of milk costs$3.89. is this an example of proportional or non proportional

Non-Proportional

Step-by-step explanation:

A proportional pricing method would ensure that the various quantities of milk have the same relative price relating to their quantity. For instance, a half gallon of milk should be half the price of a full gallon of milk for it to be Proportional.

In this example, a gallon costs $3.89. If it were proportional then a half gallon would cost;

= 3.89/2

= $1.95

It instead costs $1.99 which means that it is Non-Proportional.

(c, 0) i might be wrong so don't put full faith on my answer

check above link.

graphically?   well, you graph them both, the solutions is where they both intersect each other, since there are two solutions, meaning they will meet twice, or namely the linear will run into the quadratic curve twice, and where they meet, those x,y coordinates are the solutions to the system.