If the legs are length a and b and hyptonuse is c then
a²+b²=c²
so
if the legs are 20 and 21 and the hypotnuse is x then
20²+21²=x²
400+441=x²
841=x²
29=x
You didn't provide more information regarding triangle but from given options, it seems that triangle has ratio from shortest side to longest side would be 5 : 12 : 13
So 13 would be hypotenuse since it is longest.
Now A cannot be right angle because tangent is not defined at 90°.
Also tan(A) would be ratio of opponent side to adjacent side (think SOH CAH TOA)
So either opposite side would be 5 or 12, and adjacent side would be 12 or 5 respectively.
So the answer is either 5 / 12 or 12 / 5 but only option provided is 12/5 so that would be your answer.
Final answer: 12 / 5
1.a. 2 hours 41 minutes b. 10 hours 21 minutes
2.a. 3:10pm b. 12:42pm