Answer:

Step-by-step explanation:
To write an equation, use the slope-intercept equation:

M is the slope and b is the y-intercept.
First, find the slope by using the slope formula for when you have two points:

Rise over run is the change in the y-axis over the change in the x-axis. Substitute values:

Simplify parentheses (two negatives make a positive) and simplify:

The slope, m, is 4. Insert this information into the equation:

Now, take one of the points and insert into the slope-intercept formula:

Solve for b, the y-intercept. Simplify multiplication:

Add 20 to both sides and simplify:

The y-intercept, b, is 20. Insert this value into the equation:

Done.
<h2>
Hello!</h2>
The answers are:
3. Addition property of equality
4.
- Simplification
7. 
<h2>
Why?</h2>
To solve the problem, we need to start with the result of the second step:

So,
For the step 3:
Then, for the 3rd step, we have to apply the addition property of equality.
The addition property of equality states that if we add a term to one side of the equality, we need to add it to the other side of the equality, in order to not alterate the equality.
Then, applying the property, we have:

Adding 7 to both sides, we have:

For the step 4:
Now, for the 4th step, we have to simplify the expression:

Then, simplifying, we have:

For the step 7:
Simplificating, we divide each side of the equality by 6:

Have a nice day!
Do you need help answering a question or something?
I believe it is 510 cm because a meter equals 100 cm so 210 cm times 2 equals 410 cm then multiply 45 times 2 and get 90 cm then add 410 plus 90 and get 510 cm.