PEMDAS
10x -40 +15 = -15
-10x -10x
________________
-40 +15 = -15 - 10x
+15 +15
________________
-40 + 15 +15 = -10x
_______________
-40 + 30 = -10x
_____________
-25 = -10x
+10 +10
________
-15 = x
<em>Hopefully this all makes sense to you ☺</em>
First find x: y= -2x+4 so you take that and substitute it into your second equation -x+3(-2x+4)=-9 ---> -7x+12=-9 ---> -7x= 3 ---> x=-3/7
Now you can find y by substituting x: y=-2x+4 ---> y=-2(-3/7) +4 ---> y=
The check that hasn't been cleared is the $82.75 check.
C. a-3x=0
Equations are like a balance scale. There needs to be an “=“
The formula for perimeter is 2l+2w. Since we know l=(w-4)-9, we can substitute this into the formula.
l=w-13
2(w-13)+2w=143
2w-26+2w=143
4w=169
w=42.25 units
Hope this helps!
