Question 625242
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Formula:  If 3 numbers are in the ratio of A:B:C and have sum S, then

1st number = S×{{{A/(A+B+C)}}}
2nd number = S×{{{B/(A+B+C)}}}
3rd number = S×{{{C/(A+B+C)}}}

The three angles of a triangle are in the ratio 5:6:7 and have sum 180°, so

1st angle = 180°×{{{5/(5+6+7)}}} = 180°{{{5/18}}} = 50°
2nd angle = 180°×{{{6/(5+6+7)}}} = 180°{{{6/18}}} = 60° 
3rd angle = 180°×{{{7/(5+6+7)}}} = 180°{{{6/18}}} = 70°

Edwin</pre>