For the formula ax+b, when the number 1 is input from one side, the calculation result 7 is obtained from the other side; when the number 2 is input from one side, the calculation result 11 is obtained from the other side. When the number 3 is input from one side, what is the result?
对于算式ax+b当从一边输入数字1时，另一边得出计算结果7；当从一边输入数字2时，另一边得出计算结果11．当从一边输入数字3时，得出的结果是多少．
<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">12 + 3</gadget>
<output>15</output>

<result>15</result>