To solve this equation, we need to find the value of x.

First, let's simplify the expression inside the parentheses:

(-50 - 49 - 48 - ... + 1 + 0 + 1 + 2 + ... + 49)

This is an arithmetic series with a common difference of 1. The sum of an arithmetic series can be found using the formula:

Sn = (n/2)(a + l)

where Sn is the sum of the series, n is the number of terms, a is the first term, and l is the last term.

In this case, the first term is -50 and the last term is 49. The number of terms can be calculated by finding the difference between the last term and the first term and adding 1:

n = (49 - (-50)) + 1
= 100

Now we can substitute these values into the formula:

Sn = (100/2)(-50 + 49)
= (50)(-1)
= -50

So, the sum of the series is -50.

Now we can rewrite the equation:

-50 + x = -45

To isolate x, we can subtract -50 from both sides:

x = -45 + 50
= 5

Therefore, the value of x is 5.