I believe it is when the forces action on the object are balanced. Hope it helps!
ANSWER

EXPLANATION
The given expression is

We regroup the numerical parts to get;

Now let us simplify the negative numbers.

We now subtract 19 from 42 to get;

We can't simplify further
Hence the simplest form is:

Answer:
-8(8-7a)
Step-by-step explanation:
56a-64=-8(8-7a)
Answer:
5
Step-by-step explanation:
(-8)-(-13)= 5