Answer:
18 (or more)
Step-by-step explanation:
Let's start off by creating an inequality:
Let "r" represent one pet rock
5r > 50 + 2r
Let's cancel out the 2r on the right side of the inequality by subtracting 2r from both sides:
5r > 50 + 2r
3r > 50
Now, to isolate r, we must divide both sides by 3:
3r > 50
r > 16.7
(Since we can't sell 16.7 pet rocks, we round up to 17)
r > 17
That means that Rosa has to sell at more than 17 pet rocks (so 18 or more pet rocks) to make profit.