Okay…I've searched the forums and found several different answers on the subject that are clear as mud. I'm trying to caculate a character's strength and bonus after all factors are accounted for. The player rolled a 50 on his initial Strength. Power armor gives an automatic +20 when worn. He then rolled "Thy strength be legend" for his power armor which added another 10 on top of everything else. My issue comes when trying to figure out how Unatural Strength works. I know the character is going to be a monster in the game and that's fine. I just want to make sure I'm doing it right.

Unnatural Strength doubles the character's Strength Bonus before any additions from power armor. So if his strength is 5 the equation should look like this.

(5x2)+3=13

And when rolling against strength you would roll as if your strength was 80 (50 + 30 from armour) but the difficulties for strength tests are reduced by 10 because of the unnatural strength.

BODMAS

Brackets Orders Division Multiplication Addition Subtraction

All number crunching in the 40k RPs follows this mathematical order.

What has been posted above is correct.

His Strength Bonus would be: 13 (just as DJ states)
His Strength characteristic would be: 80 (weaing armour, only 50 out of armour)(exactly as Face eater states)