It works because 7 x 9 x 10 is the same thing as 7 x 90, since 9 x 10 is just 90. So basically he is just writing more but the answer will still be the same.
Answer:
Step-by-step explanation:
The table shows a set of x and y values, thus showing a set of points we can use to find the equation.
1) First, find the slope by using two points and substituting their x and y values into the slope formula,
. I chose (-3, 13) and (0,17), but any two points from the table will work. Use them for the formula like so:

Thus, the slope is
.
2) Next, identify the y-intercept. The y-intercept is where the line hits the y-axis. All points on the y-axis have a x value of 0. Thus, (0,17) must be the y-intercept of the line.
3) Finally, write an equation in slope-intercept form, or
format. Substitute the
and
for real values.
The
represents the slope of the equation, so substitute it for
. The
represents the y-value of the y-intercept, so substitute it for 17. This will give the following answer and equation:

U have to cross out the 10 then u have those 4 5s 5x5=25 5x5=25 25+25=50.
(My answer might be wrong so wait until other ppl answer. If I got riGhT like my thing -3-)
Answer:
No it doesn't form the triangle because when we sum up two sides the. it should exceed the this side.