how many teams have used the stadium which hosted the athletics at the 1920 summer olympics – men's 100 metres ?
SELECT DISTINCT COUNT attr_open var_uri attr_close where brack_open dbr_Athletics_at_the_1920_Summer_Olympics_–_Men's_100_metres dbp_venue var_x sep_dot var_x dbo_tenant var_uri sep_dot var_x a dbo_Stadium brack_close