Answer:
m<DEF = 8y - 6
Step-by-step explanation:
Given that: DEG = [tex](3y +4)^{o}[/tex], and FEG = [tex](5y-10)^{o}[/tex].
The given triangle is an isosceles triangle with sides DE ≅ DF.
But,
m<DEF = DEG + FEG
= [tex](3y +4)^{o}[/tex] + [tex](5y-10)^{o}[/tex]
= 3y + 4 + 5y - 10
= 8y - 6
m<DEF = 8y - 6
Therefore, the measure of < DEF is 8y - 6.