I got 36.9 degrees

We need  to  find  the other leg  =  sqrt  ( 18.9^2  - 11.4^2)  = sqrt  ( 227.25)  ≈  15.07

The  smallest angle will be  opposite  the  shortest  side

So    let theta  be  the smallest  angle...and we have  that

tan (theta)   =  shorter  leg   / longer  leg

tan (theta)  =  11.4  / sqrt (227.25)

To  find  theta  use the  arctan   and  make sure your calculator is in degree mode

So

arctan ( 11.4  /sqrt ( 227.25) )    =  theta  = 37.1°

The other leg  b = sqrt(18.9² - 11.4²)       b ≈ 15.075

sin(A) = 11.4 / 18.9

Angle  A = 37.0976018º