To simplify the expression, we first need to find a common denominator for the fractions:

-17/19 - (20/120 + 17/19)

Since 120 is a multiple of 19, we can rewrite 17/19 as 20/120:

-17/19 - (20/120 + 20/120)

Now, we can combine the fractions:

-17/19 - (40/120)

To subtract the fractions, we need to find a common denominator, which is 120:

-17/19 - (40/120) = -17/19 - (40*19/120*19) = -17/19 - 760/2280

Now, we can combine the fractions:

-17/19 - 760/2280 = (-17*2280 - 760*19) / (19*2280) = (-38760 - 14440) / 43320 = -53200 / 43320

Therefore, the simplified expression is -53200/43320.