A = 8, В = 6, F = 12, C = 16.
F = A + B + C / 0.5 E;
12 = 8 + 6 + 16 / 0.5 E;
12 = 30 / 0.5 E
30 / 0.5 E = 12
0.5 E = 30 / 12
0.5 E = 2.5
E = 5