Determining the odds of a portion of a combo handicap

[djiddish98]

I'm sure the answer for this exists in The Google, but I'm too lazy right now.

Here's the current setup:

Bodog has Netherlands +1.5 -175

Pinnacle has Netherlands +1 and +1.5 at -121
Pinnacle has Netherlands +1 at +148

From this information, could I derive a potential Pinnacle offering of +1.5 Netherlands?

Based on my very limited understanding of these handicaps, the line of "+1 and +1.5" is taking your money and betting equally on the +1 outcome and +1.5 outcome. Therefore, does the line for "+1 and +1.5" represent the average of the odds for the two single events?

So, is the correct equation here [Prob(148) + Prob(x)] / 2 = Prob(-121)?
Or do I need to do a weighted average because I'm betting on two different lines?
Or am I way off?

Thanks GL populous

Edit: It's not the average - I assume it's a slightly more difficult calculation

 

[rito]

pinny has +1.5 -180 now

 

[djiddish98]

ah - I see it at the bottom there.

Thanks.