4052 interfacaing with arduino uno
You are ignoring the value read by analogRead().  You are then using the value A0 (14) in your sum to calculate the voltage.

Instead:

int adcReading = analogRead(sensorValue0);
int voltage0 = adcReading * (5.0 / 1023.0);


Although I think what you really meant to write was, in total:

int sensorPin = A0;
int sensorValue0;//output coming from demux pins
int sensorValue1;
int sensorValue2;
int sensorValue3;

void setup() {
Serial.begin(9600);
  Serial.println("start");
  pinMode(2,OUTPUT);//selecr pins connected A,B connected to 2 and 3
  pinMode(3,OUTPUT);
}

void loop() {
  digitalWrite(2,LOW);
  digitalWrite(3,LOW);
  sensorValue0 = analogRead(sensorPin);
  float voltage0 = sensorValue0 * (5.0 / 1023.0);//Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
  Serial.print("voltage0 = ");
  Serial.println(voltage0); 
}


Note that the value sensorPin is where you read the voltage from, and sensorValue0 is where you store that reading. Also note the use of a float type to store the calculated voltage, since an int will give you only values of 0, 1, 2, 3, 4 or 5 in this situation (so, pretty meaningless really).