The average weight of X and Y is 40kg. The average weight of Y and R is 62kg and the average weight of X and R is 56kg. The weight of X is:

From the given data, we can form equations based on the sum of weights:
The average weight of X and Y is 40kg:

2
X+Y
​
=40⟹X+Y=80— (Equation 1)
The average weight of Y and R is 62kg:

2
Y+R
​
=62⟹Y+R=124— (Equation 2)
The average weight of X and R is 56kg:

2
X+R
​
=56⟹X+R=112— (Equation 3)
Adding Equation 1, Equation 2, and Equation 3:

(X+Y)+(Y+R)+(X+R)=80+124+112
2(X+Y+R)=316
X+Y+R=
2
316
​
=158— (Equation 4)
To find the weight of X, subtract Equation 2 from Equation 4:

X=(X+Y+R)−(Y+R)
X=158−124=34kg