You pretty much want to draw a random integer number between 0 and 100.
The expression to do so is int(random(101))
And you want to compare this number to the percentages of your skills.
So let's assume we have a 20% base chance disarming the bomb.
As I'm smart, it goes up to 30%
Is my random number less or equal 30 ?
If so, I have disarmed the bomb. Otherwise, it blew up in my face.
The random number likely has to be assigned to a variable (local or global) and tested against a value made up of the base chance and the addition of skills value to it.
Global var : randNum
On user action
- Set randNum to int(random(101))
Compare randNum is less or equal baseChance + smart + speed + ability