The given inequality is
3x + 1 < 10
Subtracting 1 from both sides of the inequality, we have
3x + 1 - 1 < 10 - 1
3x < 9
Dividing both sides of the equation by 3, we have
3x/3 < 9/3
x < 3
The number line is shown below
The values to the left of 3 are all less than 3. The circle is not shaded because 3 is not included in the values of x.