1. **State the problem:** We need to find the perimeter of a trapezoid with a bottom base of 11 cm, a top base of 7 cm, and two sides each measuring 8 cm. 2. **Recall the formula for the perimeter of a trapezoid:** $$\text{Perimeter} = \text{base}_1 + \text{base}_2 + \text{side}_1 + \text{side}_2$$ 3. **Substitute the given values:** $$\text{Perimeter} = 11 + 7 + 8 + 8$$ 4. **Calculate the sum:** $$11 + 7 = 18$$ $$8 + 8 = 16$$ 5. **Add these results:** $$18 + 16 = 34$$ 6. **Final answer:** The perimeter of the trapezoid is $34$ cm. Therefore, the correct choice is **b. 34 cm**.