a) tomatoes : chicken broth = 9:15 or 3:5
Tomatoes : spinach = 9:9 = 1:1
Spinach : chicken broth = 9:15 = 3:5
b) tomatoes : chicken broth = 4.5:7.5 = still 3:5
Tomatoes to spinach is still 1:1
Spinach : chicken broth 4.5:7.5 still = 3:5
Dividing all quantities by 2 doesn’t change the ratio.