Answer:
V₂ = 0.41 L 
Step-by-step explanation:
Given data:
Initial volume of balloon = 0.39 L
Initial temperature = 74 F°
Final temperature = 102 F°
Final volume = ?
Solution:
First of all we will convert the temperature into K.
(74 F° - 32) ×5/9+273.15 = 296.483 K
(102F° - 32) ×5/9+273.15 =312.039 k
Now we will apply the Charles Law. 
According to this law, The volume of given amount of a gas is directly proportional to its temperature at constant number of moles and pressure. 
Mathematical expression: 
V₁/T₁ = V₂/T₂ 
V₁ = Initial volume 
T₁ = Initial temperature 
V₂ = Final volume 
T₂ = Final temperature 
Now we will put the values in formula. 
V₁/T₁ = V₂/T₂ 
V₂ = V₁T₂/T₁ 
V₂ = 0.39 L × 312.039 K / 296.483 K
V₂ = 121.7 L.K /296.483 K
V₂ = 0.41 L