The area of the 15ft by 20ft brick patio is 300 square feet (15ft * 20ft). The cost per square foot for this patio is approximately $7.58 ($2,275 / 300 sq ft).
The area of the 12ft by 30ft brick patio is 360 square feet (12ft * 30ft). Using the cost per square foot calculated above, we can estimate that the cost of having a 12ft by 30ft brick patio installed would be approximately $2,729.20 (360 sq ft * $7.58/sq ft).
Keep in mind that this is just an estimate and the actual cost may vary depending on various factors such as location, materials used, and labor costs.