say the pot OTT is 37.5 bb's after my opp. called. I am out of position and want to lay my opp. 1.85:1 by betting out.

So: x+37.5/x = 1.85

How do i find x in a simple way?

Ty!!

I assume you meant to have parens there like
(x+37.5)/x = 1.85

So then
1.85x = x + 37.5
1.85x - x = 37.5
.85x = 37.5
x = 37/.85

Put another way, if you want to give them 1.X : 1 odds, then bet P/X. The result is, the pot odds will be
(P + P/X) : P/X
multiply both sides by X/P
X/P*(P + P/X) : 1
X*P/P + X*P/P*X : 1
X + 1 : 1

I see Ty sir!