Each of the four outside walls of the large wooden box shown above is to be covered with waterproof plastic that comes in 3-foot-wide rolls. the plastic does not overlap. what is the total length, in feet, of plastic, needed to cover the four walls?
a) 21 ft
b) 42 ft
c) 63 ft
d) 84 ft
e) 126 ft
explain too, .

We need the lateral aera
that will be
LA=2H(L+W)

H=6
L=12
W=9
LA=2(6)(12+9)
LA=12(21)
LA=252

so we need 252 square feet
it comes in 3ft width so
3ft times ?=252
divide both sides by 3ft
?=84

we need 84ft of that wrap

D is answer

x = -2 , y = 3

Step-by-step explanation:

Solve the following system:

{4 x + 5 y = 7

y = 3 x + 9

Hint: | Perform a substitution.

Substitute y = 3 x + 9 into the first equation:

{4 x + 5 (3 x + 9) = 7

y = 3 x + 9

Hint: | Expand the left hand side of the equation 4 x + 5 (3 x + 9) = 7.

4 x + 5 (3 x + 9) = (15 x + 45) + 4 x = 19 x + 45:

{19 x + 45 = 7

y = 3 x + 9

Hint: | Choose an equation and a variable to solve for.

In the first equation, look to solve for x:

{19 x + 45 = 7

y = 3 x + 9

Hint: | Isolate terms with x to the left hand side.

Subtract 45 from both sides:

{19 x = -38

y = 3 x + 9

Hint: | Solve for x.

Divide both sides by 19:

{x = -2

y = 3 x + 9

Hint: | Perform a back substitution.

Substitute x = -2 into the second equation:

 {x = -2 , y = 3