Respuesta :

180-55=125
Subtract 180 from 55 the measure of the angle
We know that the total measure of three angles are 180° because
180°(n-3) where n represent the total sides that the figure have.

Now, we had this:
55+90+angle ACB=180°
145°+angle ACB=180°
Subtract 145° from both side
Angle ACB=35°. As a result, your final answer is 35°. Hope it help!