10 < –2b or 2b + 3 > 11 represents 2 different sets of numbers.
10 < –2b can be reduced by dividing both sides by -2; you must then reverse the direction of the < sign: -5 > b, which is the interval b < -5: (-infinity, -5).
2b + 3 > 11 reduces to 2b > 8, which in turn reduces to b > 4: (4, infinity).
It may be helpful to graph these sets.
If you really do mean "10 < –2b or 2b + 3 > 11," then the "solution" is made up of two sub-intervals: b < -5 and b > 4.