SELECT "Joint Music Award" FROM table_55843 WHERE "Total" > '18' AND "Year" > '2007'
How many Joint Music Awards are there when the Total is larger than 18, in a Year after 2007?
CREATE TABLE table_55843 (
    "Year" real,
    "MRHMA" text,
    "USCA" text,
    "RTHK" text,
    "Joint Music Award" text,
    "Total" real
)