Formula writing is very logical. I read your formula to say, "When the Salary Basis Name is equal to the Salary Amount, then..." But the Salary Basis name is text, 'USHOURLY', right? And the Salary Amount would be the hourly rate of pay, or a number, correct? I don't see where text could equal a number.
Try reading up on Filter Using. Basically you want to filter your formula to only apply to workers with a salary basis = 'USHOURLY'
I'm pretty new to this forum, so I hope that I'm not speaking out turn, or giving poor advice.
By naming the subject area, I assume you're using OTBI? We don't know your data models. But your formula looks like it should be:
CASE WHEN "Salary Basis"."Salary Basis Name" ='USHOURLY' THEN "Salary History"."Salary Amount" * "Worker"."Normal Working Hours" * 26
(of course, you also need ELSE and END clauses).