You need at least 2 congruent angles , or 3 proportional sides , or 2 proportional sides and 1 congruent angle to prove that 2 triangles are similar. I presume that there should be a picture attached to this question , but if you only have 1 side in proportion ( x ) , you cannot prove the similarity of two triangles.
But if there already were two proportional sides or 1 proportional side and one congruent angle , you can prove they are similar if x = 48
