donna purchased a prepaid phone card for 20$, long distance calls cost 17 cents a minute using this card. Donna used her card only once to make a long distance call. if the remaining credit on her card is 15.07, how many minutes did her call last?

true

step-by-step explanation:

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

i think the answer is b x = 1, y = 35/2