How to calculate probaility for certain event?

Question

if the probability or doing a certain task is 60/100 with additional artificial help of 35/100. If certain modifiers are added such as a 5% penalty of the prob. then 2 other modifiers, wheter improving or decreasing the initial probability. What will be teh formula to predict the probabilty of performing that task successfully.
This is what i think let me know
(P(a)*P(b))*(C+D+E) "Where C,D,E are the modifier"

Let me expalin it in more details.
the set probability for the person performing the task is P(a). Then he must use a tool that performs at a certain probability P(b). Then we have 2 modifiers. Modifier C and D only affect the person performing the task. and modifier E affects both the person and the tool.
I hope this clears it up a bit.

Thanks,

Answer 1

I eat eggroll with 60% certain, I like duk sauce

Answer 2

I do not understand your "with additional artificial help of 35/100." I am unsure if that means (60+35)/100 [or 95%] or 60% with a + 35% modifier (or .6 * 1.35, which yields about 80%). Since the initial probability is either 80% or 95%, then the probability eq looks similar to your equation. Either;

[P(a)*(100% + P(b))] *(100%+C)*(100%+D)*(100%+E)
or
[P(a)+P(b)] *(100%+C)*(100%+D)*(100%+E)