Answer:
s = 12cm
Explanation:
Since these are similar triangles, in order to find a missing side, you have to find the constant of proportionality
14/8 = 21/s >> cross multiply
14s = 168 >> divide both sides by 14 to get s alone
s = 12
another way to find the answer......
Explanation:
You still have to find the constant of proportionality, it's just going to be a bit faster this way
14/8 = 1.75
21/1.75 = 12
s = 12