Is there supposed to me a picture or what?
I think that the missing word here is:
"with the amount of the material that Michelle has"
Let's say that her landing strip is x miles long, then its area would be:

We also know how big it is:

now, let's multiply both sides by 6:



So the answer is that it would be

miles wide
Step-by-step explanation:
wow, how complicated can one phrase this ...
the point being :
1 ft = 12 in and vice versa (1 in = 1/12 ft)
so, any measurements given in feet but needed in inches need to be multiplied by 12.
and any measurements given in inches but needed in feet need to be divided by 12.
so,
3.5 ft = 3.5×12 = 7/2 × 12 = 7×6 = 42 in
27 in = 27/12 = 9/4 = 2 1/4 or 2.25 ft
P=2l+2w
W=7+3l
So substitute into the original equation
P=2l + 2(7+3l)
78=2l +14 + 6l
-14 -14
—————-
64=8l
8=length
W=7+3l
= 7+3(8)
=7+24
=31
Check your work
Perimeter=8+8+31+31
=78
Hope this helps