WeBWorK Standalone Renderer

Here is a definition: $x \: \Box \: y = 2x+3y$ . Read it and use it to:
Find $1 \: \Box \: 7 \: =$

Find $c \:\Box \: x \:=$

Solve for $x$ if $(x+1) \: \Box \: x = 13$

$x=$

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