Question 963076
Picture is w by L and the uniform width for the frame around the picture is u.  The combined area of frame and picture is {{{(w+2u)(L+2u)=A}}}.  You are given w and L, but u is an unknown variable.  A is also given.


The area equation  {{{highlight_green((w+2u)(L+2u)=A)}}}  has only one unknown variable and this can be solved, and it is what is asked to be solved.


Solve as far as you can symbolically and choose when you wish to using w=5, L=7, A=72.