Question

Two angles in a triangle have measures of 25° and 55º.What is the measure of the third angle?A. 135B. 100C. 80°D. 30°

Answer 1

Interior angles of a triangle add up to 180 degrees, this means that

$25+55+x=180$

where x denote the third angle. Then, we get

$80+x=180$

by moving 80 to the right hand side, we have

$x=180-80$

then, the answer is x=100, which corresponds to option B