how to spawn an object in unity code example

Example: how to make % posibility to spawn an object in unity

if(Random.value > 0.5) //%50 percent chance {//code here }  if(Random.value > 0.2) //%80 percent chance (1 - 0.2 is 0.8) { //code here }  if(Random.value > 0.7) //%30 percent chance (1 - 0.7 is 0.3) { //code here }