Adding 3 html formula-involved texts fields (number of days)

So can you elaborate more ,   I understand  like

There are three formula text fields which gives the number of days as output like

[Formula 1] = 12 

[Formula 2] = 10 

[Formula 3] = 14 

On 4th field which is [Formula 4] , you need to add the 12+10+14 and show the sum as 36 in the last field . 

Is this is what you are asking !!!