Răspuns:
Explicație pas cu pas:
a = ( 28 : 7) : 2
a = 4 : 2
a = 2
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a × b = 16
2 × b = 16
b = 16 : 2
b = 8
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b : c = a
8 : c = 2
c = 8 : 2
c = 4
______________
c × d = 20
4 × d = 20
d = 20 : 4
d = 5
______________
a × b : c + d = 2 × 8 : 4 + 5 = 16 : 4 + 5 = 4 + 5 = 9