Write a system of equations to describe the situation below, solve using substitution, and fill in the blanks. Norma is making greeting cards, which she will sell by the box at an arts fair. She paid $34 for a booth at the fair, and the materials for each box of cards cost $8. She will sell the cards for $10 per box of cards. At some point, she will sell enough cards so that her sales cover her expenditures, How many cards will that take? How much will the sales and expenditures be?​