ok let us assume x= the width of the table top
the length is 4 times the width meaning we are multiplying 4 and the width
which is x
length = 4x
your first equation would be the following:
4x+4x+x+x= whatever the perimeter is
if you drew a rectangle it would help you understand the above.
this represents the perimeter of the tabletop because we know the width is x. if you drew the rectangle there wouldn't be 1 width. opposite to the width is another line. same with the length. the length is 4x again there are 2 because in a rectangle there are 2 sets of parallel lines. that is why your equation would be 4x+4x+x+x= whatever the perimeter is- you could simplify this equation and write:
10x= whatever the perimeter is
x basically means 1x but in math we generally don't write that because we tend to write most things in simplest for.
hope this helps :)