Answer:
A B X
0 0 0
0 1 1
1 0 1
1 1 1
Explanation:
If A=1, the output X is 1 as well, due to the OR gate. So that takes care of the last two rows.
If B=0, the AND gate will be 0 so it cannot contribute to X becoming 1. So that takes care of the first row (X=0).
For A=0, B=1, the AND gate will be 1, so X will be as well. You can see that the truth table matches that of a simple OR gate, X=A+B
Rather than exercising the circuit like this, you can also find this outcome algebraically:
X = (A + (A' * B)) [apply distributive law]
X = (A + A')*(A + B) [complement law]
X = 1 * (A + B)
X = A + B
