Răspuns :
folosesti egalitatea a/b = c/d => ad = bc
a) 6/x = 9/5 => 9x = 6*5 => 9x = 30 => x = 30/9 = 10/3
b) 7/5 = x/10 => 5x = 7*10 => 5x = 70 => x =70/5 = 14
c) 7/3 = 21/x => 7x = 3*21 => 7x = 63 => x = 63/7 = 9
folosesti egalitatea a/b = c/d => ad = bc
a) 6/x = 9/5 => 9x = 6*5 => 9x = 30 => x = 30/9 = 10/3
b) 7/5 = x/10 => 5x = 7*10 => 5x = 70 => x =70/5 = 14
c) 7/3 = 21/x => 7x = 3*21 => 7x = 63 => x = 63/7 = 9