The delivery person stopped on the 14th floor to talk to a friend.
before stopping, he had just made a delivery 4 floors above.
before that he made a delivery 6 floors below. before that he had
made a delivery 9 floors above. before that he had made a delivery
15 floors below. on what floor did he make his first delivery?

rectangular prism would best match the box of cards

1010: 3030

is it i think

hello from mrbilldoesmath!

answer:

(7 x + 6 y) (49 x^2 - 42 x y + 36 y^2)

discussion:

the trick is to recognize that 343 = 7^3 and 216 = 6^3 and, in general,

a^3 + b^3 =   (a + b) (a^2 - a b + b^2).

in our case

343x^3+216y^3   =   (7x)^3 + (6y)^3

so take a = 7x and b = 6y in the above equation to get the answer.

you,

mrb