Answer
x=$\square$-$\triangle$
Work Step by Step
6x-$\triangle$=7x-$\square$
First subtract 6x from both sides
-$\triangle$=7x-6x-$\square$
-$\triangle$=x-$\square$
Then add $\square$ to both sides
-$\triangle$+$\square$=x
$\square$-$\triangle$=x
x=$\square$-$\triangle$