Line Plots · Challenge problem

A line plot shows the lengths of some beads, in inches. Every bead is $\dfrac{1}{8}$, $\dfrac{3}{8}$ or $\dfrac{5}{8}$ inch long, and there are just as many X's above $\dfrac{1}{8}$ as above $\dfrac{5}{8}$. Strung together, the beads are exactly $3$ inches long. How many X's are on the plot?