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 !!!

Yes, exactly John. I want the 4th field to say "36" as the answer going by your example.

If the 4th field is a Numeric Field:
toNumber([Formula 1] )+toNumber([Formula 2] )+toNumber([Formula 3] )

If the 4th field is a Text Field:
toText(toNumber([Formula 1] )+toNumber([Formula 2] )+toNumber([Formula 3] ))

Regards

Thanks Aiden. It is working on cases where there is a value on all 3 fields. If one of them is yet to come to pass (e.g., two stages are crossed with a delay and the third stage is yet to start), the 4th field (with the above formula) is not showing any result. Can it be fixed, even if the one of the 3 stages has "null/no/0" for a value? Sometimes, we do have cases where we skip a stage and move the project right into the next one, where, only 2 stages have applicable delays and the third one might not. Thanks for your help.