A's current age is three times that of B's age at that time, and A's age at that time is the same as B's current age. If the sum of A's and B's current ages is 45 years old, then how old is A now?
甲现在的年龄是乙当年年龄的3倍，甲当年的年龄与乙现在的年龄相同，如果甲与乙现在的年龄和为45岁，那么甲现在是多少岁．
<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">45 / 5</gadget>
<output>9</output>

<gadget id="calculator">9 * 3</gadget>
<output>27</output>

<result>27</result>