Youn could test all of the options by putting 8 and 3 in for a and b.
A. a - b = 5
8 - 3 = 5
5 = 5
B. a + b = 5
8 + 3 = 5
11 ≠ 5
C. a - b = 8
8 - 3 = 8
5 ≠ 8
D. a + b = 8
8 + 3 = 8
11 ≠ 8
As you can see, the only one that works is A. a - b = 5.
Total people=180
discount received people=25%+10%=35%
People who did not receive discount=100-35%=65%
65%of 180=65×180/100=117
So 117 people did not receive discount
5% of a meter is .05 m which is 5 cm. This is less than 6cm