Mighy it go something like " Opponent I believe has 50 combos of bluffs he will bet on river if I check and 50 he will value bet so I need to check\call 50% of my value hands and lead the other 50% of value hands (I lead turn in this particular made up "example).

When you want to compare multiple actions of your own to see which is better you would compare the expected value of both actions, EV. And you take the highest EV action.
For example bet or check you would compare EVBet to EVcheck. Both off these can become very complex in a gametree, especially if there's multiple streets and more money to be played for. This is the very basic idea though.

For bluff:value ratio you need to keep in mind the betsize and the odds you are giving/being given. You want to keep in mind how often the caller needs to win to have an EV of 0. The formula is betsize/(betsize+betsize+pot). If I bet 75% then my opponent also needs to call 75% to win pot + 75% + 75%.
Example: Pot = 1. Bluff ratio: 0.75/(1+0.75+0.75) = 30%. There should be 70% value and 30% bluffs. If this ratio is broken in any way then you can exploit by overfolding or overcalling.

For the frequency on how often you want to call you want to look at how much money your opponent is risking to win how much to reach an EV of 0. Formula is bet/(pot+bet).
Example: Pot = 1. Betsize = 0.75. Formula: 0.75/(0.75+1) = 42.86%. This is how often your opponent needs you to fold for his bet to become auto profitable. So to see how often you need to call it's called Minimum defense frequency (MDF) or 1 - Alpha (1-A). Here it would be 100-42.86 = 57.14%.
If there's called less often then the bluffs gain more EV and more bluffs will be had. If there's called more then the bluffs lose value and there will be less bluffs.

This is all simplified but shows you the idea behind the math.