Răspuns:
Explicație pas cu pas:
11.
3(5a + 4b) = 2(5a + 7b)
15a + 12b = 10a + 14b
15a - 10a = 14b - 12b
5a = 2b
a/b = 2/5
_________
b/(a + b) = 1/(a/b + 1) = 1/(2/5 + 1) = 1/[(2/5 + 5/5)] = 1/(7/5) = 5/7
12.
25 patrate in total
12 patrate albe
(12/25)*100 = 48%
