[size=150][b][size=200][color=#b45f06]The [url=https://www.mathsisfun.com/definitions/sum.html]sum[/url] of the angles in a triangle is equal to a [url=https://www.mathopenref.com/anglestraight.html]straight angle[/url] (180 degrees). [/color][/size][/b][/size]

[size=200][b][color=#ff0000]We can use the fact that the sum of the angles in a triangle is 180 degrees to solve Geometry problems. [/color][/b][/size]

[color=#0000ff][b]We know the measure of two angles in a triangle. [/b][/color][math]\angle[/math][color=#0000ff][b]1 = 25[/b][/color][math]^\circ[/math][color=#0000ff][b] and [/b][math]\angle[/math][b]3 = 75[/b][/color][math]^\circ[/math][br][b][color=#0000ff]Find the number of degrees in [/color][/b][math]\angle[/math][b][color=#0000ff]2[br][br][/color][/b][b][color=#351c75]Step 1: Set up the equation[/color][/b][br][color=#ff0000][b][br][/b][/color][math]\angle[/math][color=#0000ff][b]1 + [/b][/color][math]\angle[/math][color=#0000ff][b]2 + [/b][/color][math]\angle[/math][color=#0000ff][b]3 = 180[/b][/color][math]^\circ[/math][color=#0000ff][br][br][/color][b][color=#351c75]Step 2: Rewrite the equation using the information given in the problem:[/color][/b][br][b][color=#0000ff][br]25 + [/color][/b][math]\angle[/math][b][color=#0000ff]2 + 75 = 180[/color][/b][br][br][b][color=#351c75]Step 3: Add the numbers that you can on the left of the equal sign[br][br][/color][color=#0000ff]100 + [/color][/b][math]\angle[/math][b][color=#0000ff]2 = 180[br][br][/color][/b][b][color=#351c75]Step 4: Subtract 100 from both sides [br][br][math]\angle[/math][/color][color=#0000ff]2 = 180[/color][/b]