I came across this question today and my Math 20-2 instructor expects that I know how to solve it. I have never seen a ratio like this before, I am usually using a ratio with 2 parts ($a:b = c:d$ or $\frac{a}{b}=\frac{c}{d}$). Here's how it goes:
$5:2:x = y:14:21$
I'm thinking that it needs to be changed into a linear equation? The answer key says $x = 3$ and $y = 35$. Any ideas on how to solve this? Also, what would this ratio be called?
All they're saying is that you have three pairs in ratio, not two. Using your second version, that means that $$\frac{5}{y} = \frac{2}{14} = \frac{x}{21}$$ As long as you have one "complete" fraction, you're good to go.