Question 143397
The way you have written this problem makes no sense.  Given am+cn?  am+cn equals what?  Also, was there a figure included?


Now, if you just made a mistake typing and meant:

Given {{{am=cn}}} and {{{mb=nd}}} then prove {{{ab=cd}}}, then there is no solution.  That is because with the given relations, {{{ab<>cd}}} in general.  It can be proven that {{{ad=bc}}} however.