Answer:
y = 14
Explanation:
Since this is an isosceles trapezoid, the legs are congruent. This means the expressions for AB and CD are equal:
7y - 4 = 8y - 18
Add 18 to each side:
7y - 4 + 18 = 8y - 18 + 18
7y + 14 = 8y
Subtract 7y from each side:
7y + 14 - 7y = 8y - 7y
14 = 1y
14 = y