Decomposing the vector b on the x-axis and the y-axis, we get a rectangle triangle where the two sides are bx (x-axis) and by (y-axis), and b is the hypothenuse.
The component in x, bx, is equal to the product between the hypothenuse and the cosine of the angle between b and the x-axis, which is [tex]23.5 ^{\circ}[/tex]:
[tex]b_x = b \cos (23^{\circ})=(4.00 m)(\cos (23^{\circ}))=3.68 m[/tex]