Explanation:

Total number of votes = 7500 

Given that 20% of Percentage votes were invalid

 = Valid votes = 80%

 Total valid votes = 7500*(80/100) 

1st candidate got 55% of the total valid votes. 

Hence the 2nd candidate should have got 45% of the total valid votes 

= Valid votes that 2nd candidate got = total valid votes x (45/100) 

7500*(80/100)*(45/100) = 2700

Hence, option 1 is the correct answer.