Question 407088
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Hi
x/12 divide by 7xy/4
{{{ (x/12) * (4/7xy) = 4x/(84xy) = 1/(21y)}}}

Recommend comparing the final simplification to the orignal as a final check:
{{{(x/12)/(7xy/4)}}}   |  {{{1/21y}}}

For example: 
I) The final simplification needs to include  a 'y' (cannot simply 'erase' it)
II) If one were to somehow get '40' for example in the denominator: highly
unlikely that could even be possible with the presence of the '7' originally.

In a typical 'solve for x'..type problem..so easy to check by simply substituting the value found.. 
back into the original equation as a means of checking Your answer.

When the instructions are to simplfy an expression, it's a bit more difficult 
 to 'check your answer', however, many times just 'sight checking' against
the original works well as a means of checking Your work.