How can I write a system of equations for this word problem?

Question

You're selling cards. You spend 36 dollars on paint and brushes. You buy plain cards for 3.50, then paint them and sell for 5 dollars. How many boxes must you sell for you earnings to equal your expenses and when will you break even?

Answer 1

c+p+b = 39.5

e=39.5/5

????

i think???

its been ages since i took algebra

c = cards

p = paint

b = brush

e = break even

i might have it wrong, do i have too many variables?

Answer 2

Let x be the number of cards made and sold (assume no inventory, every card you make is sold, and assume there's enough paint to make however many cards you wish.  Also, I'm not sure how the problem changed from 'cards' to 'boxes'.  Is there a given number of cards per box? I'm going to assume you make and sell individual cards)

Your money going out is 36+3.5x ($36 spent up front plus $3.50 per card)

Your money coming in is 5x (each card sells for $5

You break even when 36+3.5x=5x

Solving, 36=1.5x

x=36/1.5=24 cards.

If you make and sell exactly 24 cards, you break even.

_/