can anybody solve this.
Compute $\displaystyle \mathbb{E}(X)=\sum_{i=1}^3 x_i \mathbb{P}(X=x_i)=0.2 \times 10+0.3\times 20+0.5\times 30$
Complete the table with the values of x^2
Then compute $\displaystyle \mathbb{E}(X^2)=\sum_{i=1}^3 x_i^2 \mathbb{P}(X=x_i)$
The variance is $\displaystyle \mathbb{E}(X^2)-[\mathbb{E}(X)]^2$
That's all folks