Please help. I don’t understand this math problem.

Answer:
(7) The value of -j is 9.
(8) The value of -(-j) is -9.
(9) The value of (-j)(-j) is 81.
Step-by-step explanation :
Part 7:
Given algebraic expression is:
j = -9
Now we have to determine the value of (-j).
-j = - (-9) = 9
The value of -j is 9.
Part 8:
Given algebraic expression is:
j = -9
Now we have to determine the value of -(-j).
- (-j) = - [-(-9)] = -9
The value of -(-j) is -9.
Part 9:
Given algebraic expression is:
j = -9
Now we have to determine the value of (-j)(-j).
(-j)(-j) = [- (-9)] × [- (-9)] = 9 × 9 = 81
The value of (-j)(-j) is 81.