4x + 13y = 40
4x + 3y = -40
multiply second equation by -1
4x + 13y = 40
-4x - 3y = 40
add equations together
10y = 80
y = 8
put y in either original equation
4x + 3(8) = -40
4x + 24 = -40
subtract 24 from both sides
4x = 64
x=16
y=8
You can tell if lines are perpendicular or not by seeing if meet in a right angle. A right angle is like a square, and the lines would have to be 90 degrees.
One example is when the two lines (horizontal and vertical) meet each other at the ends.
(You MUST make sure that they are directly horizontal and vertical. If not, they will either be acute or obtuse).
I hope this helped!
c.
The number of students is represented with S, to show 2 times that number it is shown as 2S, a less than is word problem jargon for minus. So it is 2S-21.
97,531 because all of the numbers are different & odd! it’s also the highest 5 digit number that you can make with these qualities
