Substitute the value of b in the equation to check which equation satisfy the value of b.
For b + 6 = 10,

b = 3 is not solution of equation.
For b + 8 = 11,

So b = 3 is solution of equation b + 8 = 11.
For equation 5 - b = 8,

So b = 3 is not solution of equation.
For equation b - 6 = 9,

So b = 3 is not a solution of equation.
Answer: b + 8 = 11