Answer:
BC = 30
Explanation:
We know that opposite sides of a parallelogram are congruent. Because of this, we can equate their lengths and solve for the variable z:
15z = 19z - 8
↓ adding 8 to both sides
15z + 8 = 19z
↓ subtracting 15z from both sides
8 = 4z
↓ dividing both sides by 4
2 = z
z = 2
Now, we can plug this z-value into the length of side BC and simplify:
BC = 19z - 8
BC = 19(2) - 8
BC = 30