Question #39c1b

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Answer 1 · 2017-10-03T05:18:14

#c=-11#

#67=78+c#

Remove all non-variable values from the right side.
#67\color(indianred)(-78)=\cancel(78)+c\cancel(\color(indianred)(-78))#
#67-78=c#

Simplifying that, we get #c=-11#.

Answer 2 · 2017-10-03T05:19:59

#c=-11#

#67=78+c#
#67+(-78)=78+c+(-78)#
#67-78=cancel(78)+c+cancel((-78))#
#c=67-78=-11#