Answer
The distributive property was not applied properly in the first step.
$36x-7$ should have been $36x-63$.
$x=-64$
Work Step by Step
$37x+1=9(4x-7)$ $\longrightarrow$distributive property
$37x+1=36x-63$ $\longrightarrow$addition property
$37x+1-1=36x-63-1$ $\longrightarrow$simplify
$37x=36x-64$ $\longrightarrow$addition property
$37x-36x=36x-64-36x$ $\longrightarrow$simplify
$x=-64$