Rule: Adding up the three angles of any triangle always results in 180 degrees
F+U+N = 180
(x+21) + (x+23)+(x+61) = 180
x+21+x+23+x+61 = 180
(x+x+x)+(21+23+61) = 180
3x+105 = 180
3x+105-105 = 180-105
3x = 75
3x/3 = 75/3
x = 25
If x = 25, then angle N is...
N = x+61
N = 25+61
N = 86
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Answer: 86 degrees