Answer:

Explanation:
Given:
Let's answer this question by naming it.
Figure: Attachment
Iet big triangle be ABC and Small triangle be ADE.
Given:
DE = 6x + 31
BC = 19x - 36
To find : BC = 19x - 36
AE = EC
AD = DB
so,
AC = 2AE
AB = 2AD
It means the corresponding side ratio are:


Since the corresponding side's ratio is equal. it means,
ΔADE is similar to ΔABC.
As we know that,
corresponding side ratio of similar triangle are proportional, so

Substituting value of DE and BC

Doing Criss cross multiplication:

Opening bracket

Adding 36 and subtracting 12x on both sides


Dividing both side by 7, we get


Now,
BC = 19x - 36 = 19*14 -36 =230
Therefore, The numerical length of 19x - 36 is 230.