Until you specify a value for 'b', there's nothing to prove. The equation says "When 'b' is raised to the 1.3 power, the result is 18". The statement is true if b=9.23835 (rounded).
If you had just written the equation and said that b = approximately 9.23835, then in order to prove the statement, I would find (9.23835 ^ 1.3).
According to my calculator, (9.23835 ^ 1.3) = 18.00001 (rounded) .
