Answer
$(-\infty, 7)$
Refer to the graph below.
Work Step by Step
By adding $6$ to both sides we get
$$
x-6\lt 1 \Longrightarrow x-6+6\lt 1+6\Longrightarrow x\lt7
.$$
In terms of intervals, $x\in (-\infty, 7)$.
To graph, plot a hole at $x=7$ then shade the region to its left.
