Three years ago, the sum of the ages of the three students and the teacher was exactly 90 years old. This year, the sum of the ages of the three students is exactly equal to the age of the teacher. How old will the teacher be in three years?
三年前，三个学生和老师的年龄和正好是90岁，今年三个学生的年龄和正好等于老师的年龄，三年后老师多少岁？
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">90 + 12</gadget>
<output>102</output>

<gadget id="calculator">102 / 2</gadget>
<output>51</output>

<gadget id="calculator">51 + 3</gadget>
<output>54</output>

<result>54</result>