The answer is 200 because you multiply 20x12 you get 200
8 - 15 means subtract the positive number 15 from 8.
8 - 15 = 8 + (-15) = -7
8 - (-15) means subtract the negative number -15 from 8.
Subtracting a negative number is the same as adding a positive number.
8 - (-15) = 8 + 15 = 23
8 - 15 = -7, and 8 - (-15) = 23. The expressions mean different operations and have different answers.
Answer: (a) 
(b) 
(c) 
(d) 
Step-by-step explanation:
Properties of exponents :
1) 
2) 
3) 
4) 
Now , we simplify the given expression using the above properties.
a) 
[By property (1)]
[∵ (+)(-)=(-)]
b) 
[By property (3)]
[∵ (-)(-)=(+)]
c) 
[By property (2)]
[By property (4)]
d) 
[By property (3)]
