1. ## Equation of line

The line parallel to x-axis and containing the point (3,4,5)......Any suggestions ???

2. Originally Posted by Altair
The line parallel to x-axis and containing the point (3,4,5)......Any suggestions ???
The x-axis is parallel to the vector (1,0,0). That means you know already the direction of the line and one point located on the line.

Now use point-direction-form of the straight line:

$\vec r = (3,4,5) + t\cdot (1,0,0)$