Question

First, rewrite 19/21 and 8/9 so that they have a common denominator.

Answer 1

we can simply do that by multiplying each by the other's denominator.

`\cfrac{19}{21}\hspace{9em}\cfrac{8}{9} \\\\[-0.35em] ~\dotfill\\\\ \cfrac{19}{21}\cdot \cfrac{9}{9}\implies \boxed{\cfrac{171}{189}}\hspace{9em}\cfrac{8}{9}\cdot \cfrac{21}{21}\implies \boxed{\cfrac{168}{189}}`