Given triangle $ABC$ where $A$ and $B$ are on straight lines $l$ and $m$ respectively, and the measure of angle $A$ is $43°$ and angle $B$ is $47°$, what is the measure of angle $y$ (angle $C$) in degrees?

• A. $137°$
• B. $147°$
• C. $133°$
• D. $90°$

Answer: (A)

Verified step by step guidance

1. Recall that the sum of the interior angles in any triangle is always 180 degrees. This is a fundamental property of triangles.
2. Identify the given angles in the triangle: angle A is 43 degrees and angle B is 47 degrees.
3. Set up the equation for the sum of the angles: \(\text{angle A} + \text{angle B} + \text{angle C} = 180^\circ\).
4. Substitute the known values into the equation: \(43^\circ + 47^\circ + y = 180^\circ\), where \(y\) represents angle C.
5. Solve for \(y\) by isolating it on one side: \(y = 180^\circ - 43^\circ - 47^\circ\).