How to use pcall?

I want to protect my calls in case something goes wrong the whole game wouldn't be broken, but how do I get the results from the functions? For example:

function randomstuff()
a = pcall(math.random,1,100)
if a then
 print([The result])
else return false
end
end

How would I get the results from the pcall?

A more pratical use would be:

function safeaddvalue(parent,name,value,add)
    a = pcall(value.Value = value.Value + add)
    if not a then
        b = Instance.new("NumberValue",parent)
        b.name = name
        b.value = add
        return false
    else return true
    end
end

My temporary solution:

function randomstuff()
    a = pcall(b = math.random,1,100)
    if a then
        print(b)
    else return false
    end
end

Is it the correct way to do it? if not, what is?