A function is a relation that maps each value in its domain to exactly one value in its range. A rational function is a function that is a ratio of two polynomials.
The given function is a rational function as it is a ratio of two degree-one polynomials. The value of a function at a point are obtained by substituting the point in the function definition.
The given function definition is and f(5)=8. Hence, substitute x=5 in function definition and equate it to 8
Hence, the value of B is equal to 6.