Arnie bought some bagels at 20 cents each. He ate 4, and sold the rest at 30 cents each. His profit

Arnie bought some bagels at 20 cents each. He ate 4, and sold the rest at 30 cents each. His profit was $2.40. How many bagels did he buy?

Let x be the number of bagels Arnie sold. We have the following equation:
0.30(x - 4) - 0.20(4) = 2.40

Distribute and simplify:
0.30x - 1.20 - 0.8 = 2.40

Combine like terms:
0.30x - 2 = 2.40

Add 2 to each side:
0.30x = 4.40

Divide each side by 0.3
x = 14.67 ~ 15