Calculate probability of benefit does not exceed 5

A family buys two policies from the same insurance company. Losses under the two policies are independent and have continuous uni dist on the int from 0 to 10. One policy has a decutible of 1 and the other has a deductable of 2. The family experiences exactly one loss under each policy. Calculate the probability that the total benefit paid to the family does not exceed 5.

I am told this:
0<5 if X<1 and Y<2
x-1<5 X>1, and Y<2
Y-2<5 X<1 and Y<5
X+Y-3<5 X>1 Y>2

Then I am told this:
(1*7+(6-1)2+1/2*5*5)/100

My question is where are the values in the top of the fraction coming from?

Idontunderstand said:

uni dist on the int

Click to expand...

Is this text-speak? :-?

response to text-speak

Uni dist int would be uniform distributions interval


No this is the solution to May 2003 Course 1 examination problem 20, also P sample exam question problem 93, and Dr Ostaszewski's online exercise posted Sep. 26, 2009.

I do not remember how to type in Latex to make the fraction look nice.