Peter bought a shirt for 20 and sold for 30 profit and percentage?

Profit = Selling Price - Cost Price
Profit = 30 - 20 = 10

Percentage Profit = (Profit / Cost Price) * 100
Percentage Profit = (10 / 20) * 100
Percentage Profit = 0.5 * 100
Percentage Profit = 50%

Therefore, Peter made a profit of 10 and the percentage profit is 50%.

To calculate the percentage profit, we first need to find the amount of profit Peter made:

Profit = Selling Price - Cost Price
Profit = 30 - 20
Profit = 10

Now, we can calculate the percentage profit using the formula:

Percentage Profit = (Profit / Cost Price) - 100
Percentage Profit = (10 / 20) - 100
Percentage Profit = 50%

Therefore, Peter's percentage profit on the shirt is 50%.