Answer:
x = 7
Explanation:
The dashes on the lines show they are equal in length.
Therefore, by inspection of the diagram, we can see that the measures of the sides of the smaller triangle (with base 5x) are half the measures of the sides of the larger triangle (with base 70).
Therefore, creating an equation with this information:
5x = 1/2 x 70
⇒ 5x = 35
⇒ x = 7