How do I Combine 5 independent variables that are directly correlated with 1 dependent variable?

I have five qualitative variables that are directly correlated with one dependent variable (i.e. when a FICO score is less than 500, write-offs occur 8.8% of the time) How do I combine these percentages to come up with a combined likelihood of write-off?How do I Combine 5 independent variables that are directly correlated with 1 dependent variable?
Sorry, you have it backwards. The dependent variable is correlated with the independent ones. That is, f(y) is some function of f(x1), f(x2,) f(x3), f(x4) and f(x5)