-10x-8y=-20
20x+16y=4

5.1%

Step-by-step explanation:

We are told that 30 shares of Stock are purchased for $15/share..

This gives a total value of: 30 × 15 = $450.

Now,they are sold for $480 with a commission of $6. This means the final money getting to the seller is; 480 - 6 = $474.

Thus; rate of return percentage = (474 - 450)/474) × 100% = 5.06%

To the nearest tenth gives; 5.1%