Miles? I'm not sure that it'd be km (unless its not an american airline)
If there were 180 taking the survey and 95 were female, that means that there were 85 males.
Since only 21 of the males said red was their favorite color, we can write the fraction 21/85.
21 / 85 x 100 = 24.7%
24.7% of the males said red was their favorite color.
Subtract 4, subtract 2x, then divide by -2