Question

1. ( mangle tbc = 80^circ ) and ( mangle abt = 99^circ ). find ( mangle abc ).

Explanation:

Step1: Identify angle relationship

Angles \( \angle ABT \) and \( \angle TBC \) are adjacent and form \( \angle ABC \). So, \( m\angle ABC = m\angle ABT + m\angle TBC \).

Step2: Substitute values

Given \( m\angle TBC = 80^\circ \) and \( m\angle ABT = 99^\circ \), substitute into the formula: \( m\angle ABC = 99^\circ + 80^\circ \).

Step3: Calculate sum

\( 99^\circ + 80^\circ = 179^\circ \).

Answer:

\( 179^\circ \)