How much does a glass cube with a side of 5-cm weigh if 1cm of glass weighs 2 2/5 grams?

  300 grams

Step-by-step explanation:

The volume of the glass cube is ...

  V = s³ = (5 cm)³ = 125 cm³

This is 125 times the volume of a 1-cm cube, so the weight is 125 times as much:

  125 × (2 2/5 g) = 300 g

The glass cube weighs 300 grams.

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.