Basically you multiply the original length by the scale factor. So let's say there's a side length of 10 and the scale factor is .5, then you multiply 10 by .5 and get 5, that's all scale factor is . It can get larger/smaller, just depends on the number.
I would say the answer would be 105
During Distributive property, the number on the outside of the parenthesis basically gets multiplied by the numbers inside the parenthesis. In this case, you would multiply 6 by 5 and 4. When you get the products, then follow the sign that comes next. In this case, you would add the products to get a total sum. I attached a photo for further reference.
Hope this helps!