A hamburger costs 30¢ more than a hot dog and 20¢ less than a cheeseburger. If 3 hamburgers cost 75¢ less than 2 hot dogs and 2 cheeseburgers, how much does a
hamburger cost?

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.