7/9 = 42/54...when 42/54 reduces, it becomes 7/9...so this is proportional because proportions are nothing but equivalent fractions.
u could also check it this way... 12/21 = 15/24 cross multiply (21)(15) = (12)(24) 315 = 288.....these do not equal and are therefore, not proportionate
440/4 = 300/3 110 = 100....not equal, so not proportionate
120/5 = 88/4 24 = 22.....not proportionate
66/82 = 99/123 0.804 = 0.804.......these are proportional
68/172 = 43/123 0.395 = 0.349......nope, not proportional
