Operations mistake

Algebra Level 1

Vikram has been working with Order of Operations all day, and has a strong sense that

$(-a) + b = b - a,$

but doesn't know why. How many of the $11 \times 11$ ordered pairs of integers $(a, b)$ , where $a$ and $b$ are integers from 0 to 10 (inclusive) , are there, such that

$(-a) + b = b-a?$