Step 1: To solve this inequality, we first need to combine all the terms on the same side of the equation.
Step 2: To do this, we can subtract 60 from both sides of the equation:
3c – 60 ≥ 150
3c – 60 - 60 ≥ 150 - 60
3c ≥ 210
Step 3: Now we can divide both sides of the equation by 3:
3c ≥ 210
c ≥ 70
Answer: Mary needs to sell at least 70 cupcakes in order to satisfy the inequality.