The error is that he probably forgot the decimal point thus causing him to say '"hundred" instead of "and" for the decimal point.
The answer is 315 as the formula is : a+b/2•h.
It would be -8d + 3w because
-(8d -3w)
you would be multiplying the hole equation by -1
so 8d would become -8d
and -3w would become positive +3w meaning the answer is -8d +3w
Your rise over run will be -3 over 1 your going to start at the point 5 on the y-axis when your at the point 5 go down 3 then over to the right 1 keep going till it off the graph. Now do the opposite way and go up 3 from 5 and to the left 1 and keep doing that till it’s off the graph.
Hope this helps
X axis is the ones that goes left and right
(x,y)
symetric about the x axis means that the vertical distance from the x axis is the same for 2 points that are symetric about the x axis
y is height
(x,y)
(5,2)
2 is height
distance from x axis
therefor the other point is -2
(5,-2)
the other vertex is at (5,-2)
