Question

Kim is sending postcards to her family. Each postcard is rectangular with an area of 12 square inches, and the length is 4 inches more than the width. Find the length and width of each postcard. If x represents the width of each postcard, select all of the equations that could be used to solve this problem.

Answer 1

Let
x-------------> the width of each postcard
y-------------> the the length of each postcard

we know that
A=12 in²
A=x*y-------> 12=x*y-------> equation 1
y=x+4-----> equation 2
I substitute 2 in 1
12=x*y----------> 12=x*[x+4]------> 12=x²+4x------> x²+4x-12=0
 x²+4x-12=0

using a graph tool----> to resolve the second order equation
see the attached figure

the solution is
x=-6----> is not solution
x=2 in
y=x+4----> y=2+4-----> y=6 in

the answer is
the length of each postcard is 6 in
the width of each postcard is 2 in