9. 已知等差数列{an}\{a_{n}\}{an}的前nnn项和为SnS_{n}Sn,3a4−a7=73a_{4}-a_{7}=73a4−a7=7,2a7−a9=62a_{7}-a_{9}=62a7−a9=6,则S10=(S_{10}=(S10=( )))