Final answer:
To find the value of x for similar trapezoids, we use corresponding sides proportional property, making the correct proportion 8/5 = x/9.
Step-by-step explanation:
To find the value of x, we need to use the property of similar figures that says corresponding sides are proportional. Since the trapezoids are similar, the ratio of one pair of corresponding sides is equal to the ratio of another pair of corresponding sides. Therefore, the correct proportion to find the value of x is option b. 8/5 = x/9. This is because the shorter base of the smaller trapezoid (which is 5 units) is proportional to the longer base of the smaller trapezoid (which is 8 units), and this proportion should equal the ratio of the corresponding bases of the larger trapezoid, being the shorter base (x units) to its longer base (9 units).