I approached this way:
Let, Mean = m
Standard Deviation = s
From the first data we get the Mean value.
P(X < 500) = P( (Z*s + m) < 500) = 0.5
Since, graph is symmetrical on both sides and each side probability = 0.5. The first data has probability = 0.5. This means that it is transformed into P(Z < 0).
Therefore, (500 - m)/s = 0. This gives mean value = 500
Now, second data states that: P(X > 650) = 0.0227
=> P( Z*s + 500 > 650) = 0.0227
=> P( Z*s > 150) = 0.0227
=>P(Z > (150/s) ) = 0.0227
=> 0.5 - P(0 < Z < (150/s) ) = 0.0227
=> P(0 < Z < (150/s)) = 0.4773
Now consulting the Table: http://socr.ucla.edu/Applets.dir/Z-table.html
I found out that P(0 < Z < 2) = 0.4772
Thus, I concluded (150/s) = 2
s = 150/2 = 75
The Standard Deviation = 75