9) D

The gender pay gap was 9.1% in 2017. Average weekly earnings were £550.

The solution here is to divide 9.1% by 2 first which is 4.55%.
Then subtract 4.5% of 550 from 550 to get £525.

The logic behind this solution:

To obtain an average of £550, we would have to add women’s earnings and men’s earnings and divide it by 2.

Let us say men earned X per week
Therefore women earned = X – 0.091X = 0.909X per week (0.091 is 9.1%)

Let us form an equation.

X + 0.909X

So men earned around about £576.
Therefore women earned = 0.909 x £576 ≈ £525

It would not be possible to do these calculations during the exam due to time restrictions but just remember that this is how the answer is arrived at.