I have a stamp collection. 70% of my stamps are Canadian and 30% are international. I have 500 more Canadian stamps than international. How many stamps do I have altogether? How many Canadian and how many international?

N= 375, C= 875

Step-by-step explanation:  Let Canadian stamps=C

Let International stamps=N

C=875     and        N=375

C - 500=N,  .70(N + C) =C

Solve the following system:

{C-500 = N |     (equation 1)

0.7 (C+N) = C |     (equation 2)

Express the system in standard form:

{-N+C = 500 |     (equation 1)

0.7 N-0.3 C = 0 |     (equation 2)

Add 0.7 × (equation 1) to equation 2:

{-N+C = 500 |     (equation 1)

0 N+0.4 C = 350 |     (equation 2)

Divide equation 2 by 0.4:

{-N+C = 500 |     (equation 1)

0. N+C = 875. |     (equation 2)

Subtract equation 2 from equation 1:

{-N+0 C = -375. |     (equation 1)

0 N+C = 875. |     (equation 2)

Multiply equation 1 by -1:

{N+0 C = 375. |     (equation 1)

0 N+C = 875. |     (equation 2)

Collect results:

|  N = 375        and             C=875

hello from mrbilldoesmath!

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

discussion:

in general, the factorization of a^3 + b^3 is

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

in our case note that 343 = 7^3 and 216 = 6^3 so the equation becomes:

343x^3 + 216y^3 = (7x)^3 + (6y)^3

if you think of a (above) as 7x and b as 6y the factorization becomes

343x^3 + 216y^3 =

((7x + 6y) (   (7x)^2 - 7x*6y + (6y)^2)   =

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

you,

mrb

(a + b) (a^2 - a b + b^2)