The wording could be better, but if we start with T employees, 35% of whom are senior engineers, then we start with 0.35T = (7/20)T senior engineers. We know a quarter of these engineers are fired, so the number of engineers and the total number of employees both drop by (1/4)(0.35T) = (7/80)T. So now we will have (21/80)T engineers left, and a total of (73/80)T employees left. Dividing the first number by the second, the 'T' will cancel, and we'll get a numerical answer to the question "how many remaining employees are senior engineers?". So Statement 2 is sufficient. We don't care how many employees there are, so Statement 1 is not useful and the answer is B.

I'd add that if you do use both Statements, you find they fired a non-integer number of employees (they would have fired 3937.5 employees), which makes no sense. It always must make sense when you consider both statements together, so the question is not well-designed.