Răspuns:
Explicație pas cu pas:
Mihai + David + Radu
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Mihai + David = 55
Mihai + Radu = 77
David + Radu = 90
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Mihai + David + Radu = ( 55 + 77 + 90 ) : 2 = 222 : 2 = 111 cartonase
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Cate cartonase are Mihai?
111 - 90 = 21 cartonase are Mihai
Cate cartonase are David?
55 - 21 = 34 cartonase are David
Cate cartonase are Radu?
90 - 34 = 56 cartonase are Radu
m + d = 55
m + r = 77
d + r = 90
m + d + m + r = 55 + 77
2 × m + d + r = 132
2 × m + 90 = 132
2 × m = 132 - 90
2 × m = 42
m = 42 : 2
m = 21
d = 55 - 21
d = 34
r = 90 - 34
r = 56
