Tarzan Swims a distance of 1.5 km at an average speed of 2.5 km/h, cycles 40 km in 1 and 1/2 and runs at an average speed of 9km/h for1 1/9h. find the average speed of all.

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.

6mm^3 or .6cm^3

      216

      /   \

  36     6

  /   \     /

6     6   6

factor trees are nice.