Answer
See below.
Work Step by Step
By definition, the expected value is the sum of each outcome multiplied by its probability.
Hence here the expected value: $\frac{1}{6}\cdot(1-1.25)+\frac{1}{6}\cdot(2-1.25)+\frac{1}{6}\cdot(3-1.25)+\frac{3}{6}\cdot(-1.25)=-\frac{1}{4}$.
This means that in the long run a player is expected to lose $\frac{1}{4}$ each turn he plays on average.
