1. f+b=28
[tex]f = \frac{75}{100} \times b \\ f = \frac{3b}{4} \\ \frac{3b}{4} + b = 28 \\ 3b + 4b = 28 \times 4 \\ 7b = 28 \times 4 \\ b = \frac{28 \times 4}{7} \\ b = 4 \times 4 \\ b = 16 \\ f = 28 - 16 \\ f = 12[/tex]
2. f+b=23
[tex]f = \frac{30}{100} \times b + b \\ f = \frac{3b}{10} + b \\ 10f = 3b + 10b \\ 10f = 13b \\ f = \frac{13b}{10} \\ \frac{13b}{10} + b = 23 \\ 13b + 10b = 230 \\ 23b = 230 \\ b = 10 \\ f = 13[/tex]
3. f+b=200
a=7b
7b+b=200
8b=200
b=25
a=175
4.
[tex] \frac{1}{2} \times elevi = algebra \\ \frac{1}{4} \times elevi = geometrie \\ = > \frac{1}{4} \times elevi = restul \\ \frac{1e}{2} + \frac{1e}{4} + \frac{1e}{7} + 3 = e \\ 14e + 7e + 4e + 3 \times 28 = 28e \\ 25e + 3 \times 28 = 28e \\ 3e = 3 \times 28 \\ e = 28[/tex]
