You have some trading cards. You give 21 cards to a friend and have 9 left for yourself. How many cards were in your original deck?

The answer is here

Step-by-step explanation:

http://assets.pearsonschool.com/file-vault/flipbooks/texasreview/mathematics/digits/TX_Digits_HomeworkHelper_HTML_Files/Grade%206/Volume%201/page_217.html

30

Step-by-step explanation:

21 + 9 = 30

the diameter is 16 cm. are you a teacher?

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