Question 970780
Multiply each X value with its corresponding probability (P or P(X) value).


2*0.2 = 0.40
4*0.1 = 0.40
5*0.25 = 1.25
7*0.05 = 0.35
10*0.4 = 4.00


Then add up the products: 


0.40+0.40+1.25+0.35+4.00 = 6.4


The expected value is <font color="red">6.4</font>


Side Note: a compact way to state the formula (without much words) is to write *[Tex \LARGE E(X) = \sum x*P(x)].