Răspuns:
Explicație pas cu pas:
a/b = 4/9
a = 4b/9
7a + b = 28b/9 + b = 28b/9 + 9b/9 = 37b/9
9 + 6b = ?
probail era 9a + 6b = 36b/9 + 6b = 4b + 6b = 10b
(7a + b)/(9a + 6b) = 37b/9 : 10b = 37/90
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2(4a + 9) = 3(5b + 6)
8a + 18 = 15b + 18
8a = 15b
a/b = 15/8
