(n-1)+n+(n+1)
With n as the middle of 3 integers, n-1 is the integer just before n and n+1 is the integer just after n.
Let Benny's salary = $ K
But kenny earns 142% of Benny's Salary
So, Kenny's salary = 142%of K
Kenny's salary =K 
Kenny's salary = 1.42K
Kenny's income exceeds Benny's by =1.42K - K =$0.42 K
% by which Kenny's salary exceeds by Benny's =
% by which Kenny's salary exceeds by Benny's = 42%