A survey of employers found that during 1993 employment cost

Can you link the method that you used?

This is how I did it:

Givens:
Fringe benefits = 5.5%
Salary = 3%
Total = 3.5%

Let X be the percentage fringe benefits represents out of total employment costs
Let Y be the percentage that salary represents out of total employment costs
The question asks you what X is

X*5.5% + Y*3% = 3.5% | should be obvious
X + Y = 100% | should be obvious
Y = 100% - X | equation to substitute out Y since we're solving for X

X*5.5% + (100% - X)3% = 3.5% | substitute out Y
5.5%X + 3% - 3%X = 3.5% | multiply the parenthesis
2.5%X = 0.5% | subtract 3% from both sides and add the X
X = 20% | multiply both sides by 40

Hence B