Question 589327
Let me define the distributive property.

Distributive property is a(b + c) = ab + ac.  

What the above law means is to multiply every item inside a parentheses or bracket by the number or letter that is "standing" outside.

However, in your question, there is no need to apply the distributive property.

Inside the parentheses we have (-2-4) = (-6).

We now multiply (-6) by (-10) to get 60.

The answer is choice a.

If you want to use the law, then we do it this way:

(-2-4)(-10) = (-2)(-10) + (-4)(-10) = 20 + 40 = 60.

Understand?