Answer:

1.

20 = x + y

x = shorter piece

y = longer piece

2x = 4 + y : rearrange as 2x - y = 4

Add the second equation to the first

x + 2x + y + -y = 20 + 4

3x = 24

3x/3 = 24/3

x = 8 ft is the shorter piece

2.

Perimeter(p) of a rectangle=2*Length(l) + 2*Width(w)or p=2l+2w

Let w=width

Then length(l)=2*w-10

p=2(2w-10)+2w=400 get rid of parens (distributive law)

400=4w-20+2w add 20 to both sides

400+20=4w-20+20+2w collect like terms

420=6w divide both sides by 6

w=70 meters-width

2w-10=2*70-10=140-10=130 meters length

400=2*70+2*130

400=140+260

400=400