Recall that a supplementary angle is an angle with which a straight angle is formed. That is, two angles are supplementary if their sum is 180º.
The statement also tells us that the lines "t" and "n" are parallel, therefore we can say that the angle m<8 and m<4 are identical.
Since in the line array we can see that the angle m<7 and m<8 are supplementary angles, that is to say, that they add up to 180°.
That is to say that the angles m<7 and m<4 also add up to 180 degrees.
