An equation between two variables that gives a straight line when plotted on a graph.

From the question it is given that,

$5x+3x<18-3x$

So, by transposing we get,

$5x+3x<18+14$

$8x<32$

$x<32/8$

$x<4$

As per the condition given in the question, $xisx\in w$

Therefore, solution set $x=\{0,1,2,3\}$