The two angles are adjacent (right next to) each other and make up the measure of the line (180°). Therefore, we can add the two angles because their sum is the measure of the straight line they lie on, which is 180° because straight lines measure 180°. Therefore angle measure 15t° added to (20t+5)° should equal 180°.
Equation:
(15t)°+(20t+5)°=180°
Simplify via the associative property of addition:
15t+20t+5=180°
35t+5=180°
Thus, the correct answer is choice B: 35t+5=180