She has a fixed cost $35 for the day.
Then on each pair of earrings, she spends $2.
Her costs are fixed $35 and $2 per pair of earrings.
She sells each pair of earrings for $5.
Her earnings are $5 per pair of earrings.
Let x = the number of pairs of earrings she sells in one day
[tex] 5x - 35 - 2x \ge 200 [/tex]
[tex] 3x - 35 \ge 200 [/tex]
[tex] 3x \ge 235 [/tex]
[tex] 3x \ge 78.333... [/tex]
Since she must sell a whole number of pairs of earrings, she must sell at least 79 pairs of earrings.