"I think my problem in understanding all this is that in most Bio's I have invested in the past, the Placebo results were pretty constant."

Sure. One can approximate a projected placebo MACE rate. However, it's never going to be exactly the same between trials even if they have similar recruitment criteria. Not too many CVOTs have had inclusion criteria of type 2 diabetes with ACS event w/i 90 days. ClinicalTrials.gov listing reads "CAD event of either unstable angina or myocardial infarction 7-90 days prior Visit 1." EXAMINE may be the only recent trial that had that matching recruitment criteria. The ELIXA trial in patients with T2D required ACS event w/i 180 days and observed event rates of ~6.3 per 100 patient years as opposed to EXAMINE that observed closer to ~8 per 100 patient years. So w/i 90 days in one trial was ~8%; w/i 180 days in one trial was ~6.3%. Hard to put too much certainty on a low number of trial observations. Plus, both ELIXA and EXAMINE ran between 2009 and 2013, so hard to say if in the 6 years between ELIXA/EXAMINE trial start and BETonMACE trial start that standard of care did or did not change. Add on to that the additional low-HDL requirement of BETonMACE. 

"In the BETonMACE the placebo results are an unknown going in, so when we get info that the MACE events are at 7.2% as of june 2018,...we still cannot figure out what MACE event rate is for our drug,..."

That's the point of running a blinded clinical trial. No peeking!

"But if we were to assume that the Placebo results are actually around 11%-12% percent in this trial,... and we assume also that the 7.2% MACE event rate is coorect as of June 2018,... with that info and those assumptions,... is it possible to calculate the RRR% of RVX-208,... would it be close to 30%,..?"

I think you are confusing annual event rates with event rates at median duration of drug expsoure. RRR calculations are easy. Divide drug event rate by placebo event rate, and subtract from 1, then multiply by 100 to get %RRR. Here are some examples that are all consistent with average annual event rate of 7.2% (I did a little bit of rounding). The following are all hypothetical apabetalone vs. placebo:

7.2% vs. 7.2% = 1.0; 0% RRR

6.7% vs. 7.7% = 0.87; 13% RRR

6.2% vs. 8.2% = 0.76; 24% RRR

5.7% vs. 8.7% = 0.66; 34% RRR

5.2% vs. 9.2% = 0.56; 44% RRR

4.7% vs. 9.7% = 0.48; 52% RRR

4.2% vs. 10.2% = 0.41; 59% RRR

3.7% vs. 10.7% = 0.35; 65% RRR

3.2% vs. 11.2% = 0.29; 71% RRR

2.7% vs. 11.7% = 0.23; 77% RRR

2.2% vs. 12.2% = 0.18; 82% RRR

BDAZ