Which equation is not linear?

first one

Step-by-step explanation:

option a

Step-by-step explanation:

as 145 +10 = 155°

and total angle measure of triangle is 180

so

180-155 = 25°

in option a one angle is 10

other is 25 so obviously last angle will be 145

and same is in the triangle abc

one angle is 10 other is 145 and last is 25

both hve same measures thus are same triangles.