Angle R is the reference angle as its the only given angle (other than the 90 degree angle).
Opposite angle R is segment PQ
PR is the hypotenuse
Use the sine rule to find that...
sin(angle) = opposite/hypotenuse
sin(R) = PQ/PR
sin(19) = PQ/11
11*sin(19) = PQ
PQ = 11*sin(19)
PQ = 3.58124969902872 <<-- use a calculator (degree mode)
PQ = 3.58
Answer: 3.58