how i controlling given algorithm speed mechanism speed?

i'm now operative by an assignment deals big-o controlling times. i have doubt presented me seems unequivocally easy, nonetheless i'm certain i'm doing correctly. rest problems have definitely difficult, i feel i'm unaware something here.

first, have things:
algorithm a, controlling 50n^3.
computer a, speed 1 millisecond per operation.
computer b, speed 2 milliseconds per operation.
an instance distance 300.

i wish enlarged takes algorithm solve instance mechanism a, enlarged takes mechanism b.

what i wish servant 300 n, have 50*(300^2) = 4500000.

then, greaten 1 initial computer, 2 second computer.

this feels rare me, though, since says "running time" 50n^3, not, "the array operations 50n^3", i feeling i'm augmenting time, finish adult units milliseconds squared, doesn't seem right during all.

i know i'm right, not, doubt indeed means.