The subjects of this year's college entrance examination include Chinese, mathematics, foreign language, physics, chemistry, biology, history, geography, and politics. Among them, Chinese, Mathematics, and Foreign Language are compulsory, and only two of the remaining six subjects are optional. If a student takes the college entrance examination this year, how many different choices will he have?
今年高考的科目有语文、数学、外语、物理、化学、生物、历史、地理、政治．其中语文、数学、外语三科必考，其余6科中只要选考两科．一位学生今年参加高考，他将有多少种不同的选择．
<gadget id="calculator">5 + 4 + 3 + 2 + 1</gadget>
<output>15</output>

<result>15</result>