I don't know what to do for this question. There are two i already did the second one its the one i circled I don't get. Please if u can show me step by step.

Answer:
x = 6 cm
Step-by-step explanation:
X is the midsegment of the triangle.
A midsegment of a triangle is always half the base.
12/2 = 6
x = 6
You can search up "triangle midsegment theorem" if you are not familiar with it.