Well in your example you already have a straight lol, but we'll use an OESD as the example here.
Your first part is correct. You have roughly 17% equity.
To do the second part, you have to figure out how often you need to win to break even given the wager laid before you. In your example you are being asked to wager .20 to win .82 (usually expressed as .82:.20 or simplified to 4:1) . There's a couple ways you can go about doing this.
A) You can convert your equity to a ratio as well and compare them that way. 17% works out to about 4.8:1. Math behind it :
(100% / 17%) - 1 = 4.8
B) You can convert the risk/reward ratio to a % and compare it to your equity. .82:.20 or 4:1 is ~20%. Math behind it :
.20 / (.20+.82) = .196 or ~20%
So if your equity is greater than the pot odds
you are being laid, you can continue. In this case, we only have 17% equity but are contributing 20% of the pot, or we are 4.8:1 against to make our hand and are only being offered 4:1.
This of course does not take action on future streets (implied odds) in to consideration, which is a whole new can of worms.