Răspuns :
suma unghiurilor unui triunghi este 180grade
A/3=B/5=C/7
A=3B/5
C=7B/5
3B/5+B+7B/5=180 aducem la acesi numitor -5
3B+5B+7B=5*180=> 15B=900=> B=60grade
A=3*60/5=> A=36grade
C=7*60/5=> C=84grade
x/3=y/5=z/7
x=3B/5
z=7B/5
3x/5+y+7z/5=180
3x+5y+7z=5*180=> 15B=900=> y=60grade
x=3*60/5=> A=36grade
X=7*60/5=> C=84grade