x-20%x-10%(20%x)=720 lei
x-0,2x-0,02x=720
0,78x=720
x=720/0,78
x=923,07 ~923 lei era prețul initial.
D+a+b=180°; D=90°; a+b=90°
a/b=0,4(2)/0,2(4)
a=90-b
(90-b)/b=38/90 ÷ 22/90
(90-b)/b=38/22
22(90-b)=38b
1980=60b
b=198/6
b=33° m(<DAN)
a=90-33
a=57° m(<DNA)
x/y=2/3; y/z=5/4
x+y+z=185
x=2y/3
z=4y/5
2y/3+y+4y/5=185
(10y+15y+12y)/15=185
37y=185×15
y=2775/37
y=75
x=2×75/3=50
z=4×75/5=60
75+50+60=110+75=185
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