ANSWER
[tex]y = 5[/tex]
EXPLANATION
The given isosceles tra-pezoid has legs
[tex]ab = - 3y + 54[/tex]
and
[tex]cd = 6y + 9[/tex]
The base is bc=5y+2.
The length of the legs of the isosceles tra-pezoid are equal.
This implies that,
[tex]ab = cd[/tex]
Thus,
[tex] - 3y + 54 = 6y + 9[/tex]
Group similar terms,
[tex]54 - 9 = 6y + 3y[/tex]
[tex]45 = 9y[/tex]
Divide both sides by 9.
[tex]y = \frac{45}{9} [/tex]
[tex]y = 5[/tex]