a rhombus is just a parallelogram, but distinct from other parallelograms, a rhombus, though its sides may be slanted, the length of each side is exactly the same.
now, what's the length of that segment from (2,5) to (-1,3)?
![\bf \textit{distance between 2 points}\\ \quad \\ \begin{array}{lllll} &x_1&y_1&x_2&y_2\\ % (a,b) &({{ 2}}\quad ,&{{ 5}})\quad % (c,d) &({{ -1}}\quad ,&{{ 3}}) \end{array}\qquad % distance value d = \sqrt{({{ x_2}}-{{ x_1}})^2 + ({{ y_2}}-{{ y_1}})^2} \\\\\\ d=√((-1-2)^2+(3-5)^2)\implies d=√((-3)^2+(-2)^2) \\\\\\ d=√(9+4)\implies d=√(13)]()
now, that's just that one side, however, all 4 sides in a rhombus are the same length, therefore, its perimeter is just that added four times.