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A+b=c=2xd+a=b+d-a=75=90-a

Răspuns :

a = 90-75
a = 15

b= 75-15
b=60

c=75

2d = 75-15
2d= 60
d=30
a= 90-75=15
b= 75-15=60
c=60
d²=75-15=60
d²=60:2=30