Is -1/3 - 4/5 positive, negative, or zero

It's not zero. Zero can only be produced in adding or subtracting when two equal numbers with opposite signs are added or subtracted. -4 + 4 would give 0.  Really tricky things like - 5 - (- 5) would be 0 because the 2 minus signs would give a plus.

-5 + 5 = 0

It's not positive either. Think money. If you owe someone 5 dollars and you put another 6 dollars on a credit card, your net worth isn't going up into the positive. It going down further into the negative. You wouldn't be alone. The US government does this every day. -5 - 6 = - 11

So  - 1/3 - 4/5 is  negative.

The answer is (though you haven't asked for it)

- 5/15 - 12/15 = - 17/15

85.560%

step-by-step explanation:

conditional probability is defined as:

p(a|b) = p(a∩b) / p(b)

in other words, the probability that a occurs, given that b has occurred = the probability that both a and b occur / the probability that b occurs.

in this example:

p(turns 64 | turns 44) = p(turns 64 & turns 44) / p(turns 44).

if someone turns 64, they must have already turned 44, so:

p(turns 64 | turns 44) = p(turns 64) / p(turns 44)

on page 42, we see that of the original 100,000, 94944 turn 44, and 81234 turn 64.   therefore:

p(turns 64 | turns 44) = 81234 / 94944

p(turns 64 | turns 44) = 0.85560