Pls help need help been working for like 30 min stilll cant get it

128

Step-by-step explanation:

the insides of a triangle always add up to 180.

12+40=52

180-52=128

last option

step-by-step explanation:

given that δdef is right and isoceles,

assuming that side df is the hypotenuse means that de an ef are the other 2 sides that intersect at 90° and are of equal length.

because they are of equal length, we can say that they are congruent

because they intersect at 90°, their slopes must be opposite reciprocals.

only the last option satisfies these conditions.

a - base

b - exponent

so,