The first number in the ratios will be the numerator and the other the denominator.
[tex] \frac{12}{15} = \frac{3*4}{3*5} = \frac{4}{5} [/tex] ←Cancel out GCF
[tex] \frac{24}{9} = \frac{3*8}{3*3}= \frac{8}{3} [/tex] ← Cancel out GCF
[tex] \frac{14 tetras}{6 angelfish} = \frac{2*7 tetras}{2*3 angelfish} = \frac{7 tetras}{3 angelfish} [/tex]