Concept:The question tests primarily on races from the area of rates
Approach 1- 
In the second instance, Jerry covers only half the distance (1000 m) while Tom covers the full distance (2000m) with additional 3 min

Let the time taken for Jerry to cover half the distance be x, and therefore to cover full distance he will take 2x

Hence Tom covers the full distance in x + 3

Therefore your answer choice must be of the form (2x, x+3)
 =>(option b)
Equation based approach-
First Race
Speed of Tom = 2000/x m/s
Speed of Jerry = 1800/ (x+30) m/s
Second Race:
Speed of Tom = 1000/y m/s
Speed of Jerry= 2000/(180+y)m/s

 Equate the speeds now
2000/x = 1000/y
=> y=x/2

 1800/(x+30) = 2000/(180+y)
=>1800/(x+30) = 4000/(360+x)  (Using y =x/2)
=> 648000 + 1800x = 4000x + 120000
=> 2200x = 526000
=> x = 239 seconds
=>Tom will complete 2000m race in 2000/239 = 3.98 ~= 4 minutes.

     Speed of Jerry is 1800 / (239+30) = 6.69 m/s
=> The time required for Jerry to finish 2000m = 2000/6.69 = 298.95 s

Therefore, the time required in minutes = 298.95/60 = 4.98 ~= 5 minutes.

 (option b)