The average weight of Sourabh, Juana and Rina is 90kg. If the average weight of Sourabh and Juana be 69kg and that of Juana and Rina be 94kg, then the weight of Juana is:

Let the weights of Sourabh, Juana, and Rina be represented by S, J, and R respectively.
From the first condition, the average weight of all three is 90kg:

3
S+J+R
​
=90⟹S+J+R=270— (Equation 1)
From the second condition, the average weight of Sourabh and Juana is 69kg:

2
S+J
​
=69⟹S+J=138— (Equation 2)
From the third condition, the average weight of Juana and Rina is 94kg:

2
J+R
​
=94⟹J+R=188— (Equation 3)
Now, add Equation 2 and Equation 3:

(S+J)+(J+R)=138+188
S+2J+R=326— (Equation 4)
Subtract Equation 1 from Equation 4 to find the weight of Juana (J):

(S+2J+R)−(S+J+R)=326−270
J=56
Thus, the weight of Juana is 56kg.