L=2W+5 or length is equal to 5 more than 2 times the width.

so back to the original equation at the top

you know now what L equals, look at the second equation

so substitute the second equation where ever you see an L

Like this (2w+5) +w+(2w+5)+w=100

Now collect like terms

6w+10=100

Subtract 10 from both sides

6w=90

divide both sides by 6

w=15

So the width is 15

so now go back to the original equation at the top.

What is w? Well you know that w=15

So… L+15+L+15=100

Again collect like terms

2L+30=100

Subtract 30 from both sides

2L=70

Divide both sides by 2

and L=35

So L=35 and w=15

the check is

35+15+35+15=100

100=100

It works

Have a Grateful day

Mike

4x=90

x= 22.5

so the length is 27.5 and the width is 22.5