How does 9+10=21? is is true or

9 + 10 does NOT equal 21. It is just a run-on joke about an African-American boy answering a question given by the cameraman, asking what 9 + 10 is. The boy says it is 21, and it has been a joke that has gone on for too long

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.