Since one red box weighs 15.2 ounces, three red boxes weigh 45.6 ounces. This is the same as two blue boxes, so we have the equation 2b=45.6 where b represents the weight of the blue box. Solving the equation by multiplying both sides by 1/2 gives us 22.8 ounces.
Tell me if this is fine. I wasn't able to edit the document you gave me, so i made one on my own. If you require a full graph, comment, and ill make it again. (I put 2, select the best one)
