Answer:
25
Step-by-step explanation:
Upon looking at the two triangles, they seem to be a reflection of each other where EF is the larger version of AB, DF of AC and BC of DE.
Knowing that, you can see that angle C is the same as angle D, which means angle E will be the same as B. This can be proven with the fact that the total angle of a triangle is 180*. So for the smalle triangle, angle B is 180-68-38 = 74. The fact that the angle is the same further proves that both triangles are the same, but are at different scales. To find x, just find what two sides are given that are the same. So AB and EF are the same, and their value are 6 and 15. And since x is DE, that would relate to BC which is 10.
So its all about cross multiplication and division
6/10 = 15/x
= 25
