Answer: The correr solution is 
Step-by-step explanation:
Since the steps in Lin's solution are not shown, we are not able to find her erros. However, we can solve it step by step and find the correct result:

Firstly, in the left part of the equation we have to multiply
by the numbers inside the parenthesis; and in the right side we have to solve first what is inside the parenthesis:

Adding similar terms in the left side and multiplying
by the number inside the parenthesis in the right side:

Isolating
:
This is the correct solution
Answer:
0
Step-by-step explanation:
x2 +4x-21=0. solve for x


Answer:
- points on the boundary line: (0, 10), (20, 0)
- solution points not on the boundary line: (100, 100)
Step-by-step explanation:
We cannot tell from the posted picture whether the boundary line is solid or dashed, so the answer above is split into two parts. If the boundary line is solid (x+2y≥20), all three listed points are in the solution set. If the boundary line is dashed (x+2y>20), only (100, 100) is in the solution set.
Answer: For the model one it’s option 1 and for the other one it’s 10,000
Step-by-step explanation: