Question 1000004
The middles line-up vertically.  Your thinking seems good.


Wall length, {{{120&3/4}}} inches.  Middle of wall is  {{{60&3/8}}} inches from either side of the wall.


Picture length, {{{32&1/2}}} inches.  Either half length of the picture is {{{16&1/4}}} inches.


DRAW a picture of all this to understand more clearly and visually.
Starting at wall middle of {{{60&3/8}}}, move to the left by half the picture length, meaning  {{{60&3/8-16&1/4}}} inches.  This is where the left side will be from the edge of the left side of the wall.  Do this in practice correctly accurately and the right sides will be the correct distances from their sides also.


{{{60&3/8-16&1/4}}}

{{{60&3/8-16&2/4}}}

{{{60&1/8-16}}}

{{{highlight(44&1/8)}}}, distance between side of wall and corresponding side of picture.


The arithmetic can look better if done ON PAPER or chalkboard.



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You had no real reason, nor need to convert into decimal numbers.  Keeping as "mixed numbers" should have been no trouble.