Order of Operations w/ Rational Numbers

Omar played a math game and had cards with the five values shown below.

7 , 1 , -5 , 2 , -10

His score was the sum of the numbers on these five cards. What was Omar's score?

Simplify:

-8 ( -3 + -10 ) + (-5)

What value is equivalent to:
 $5\ \times12\times3\div\left(-6^2\right)$  

One of Ms. W's students were working on a homework problem:
 $-2\left(8-10\right)^2+4\div-6$  

They showed their work
 $-2\left(-2\right)^2+4\ \div-6$  
 $-2\left(-4\right)+3\div-6$  
 $8+3\div-6$  
 $8+-\frac{1}{2}$  
 $=\ 7\ \frac{1}{2}$  

Can you identify the mistake?

-7w² + 2w if w = -4

12x ÷ 4y if x = -8 and y = 3