The rate of disappearance of hbr in the gas phase reaction 2hbr (g) → h2 (g) + br2 (g) is 0.190 m s–1 at 150 °c. the rate of appearance of br2 is m s–1

According to the balanced equation of this reaction :
2HBr(g) → H2(g) + Br2(g)

when we have the coefficient of the reactant is 2 and when the rate of disappearance is 0.19 m,
So the rate of appearance = the rate of disappearance^(the coefficient of the reactant)
                   = 0.19^2 
                   =0.0361 m.S^-1

Ibelieve your answer is true 

It is 4.92 e-4 sorry if i am wrong