Kailey is making earrings to sell at a local market. She spends $80 on supplies and decides to keep 4 pairs of earrings to give to her friends. Kailey sells the rest of the earrings she made for $175, making a profit of $9 per pair of earrings. If n represents the number of pairs of earrings Kailey made, then an equation that represents this information is: 9 = (175/n-4) - 80/n

Identify all restrictions on the variable n in this context