We have heat lost by water is equal to heat gained by Juice.
Heat exchanged is calculated using the formula,
[tex] \Delta H=ms \Delta T [/tex]
Let [tex] T_f [/tex] be the final temperature then,
[tex] (1)(3)(T_f-10)=(1)(4.187)(15-T_f)\\
3T_f-30=62.805-4.187T_f\\
7.187T_f=92.805\\
T_f=12.913 K [/tex]
The final temperature of the juice is 12.913 K.