Answer
Александр
The correct choice:
7.6 %.
Suppose John's original salary was "Z", then on Monday his salary was:
Z * (1 + 0.2) = 1.2 * Z
On Tuesday, John's salary was:
1.2 * Z * (1 + 0.1) = 1.32 * Z
After renting the apartment, that leaves:
1.32 * Z * (1 - 0.3) = 0.924 * Z
Thus, the amount of money for free use is from salary to all raises:
((0.924 * Z) / Z) * 100 = 92.4%
Consequently, John's amount of free use money relative to wages before all raises decreased by:
100% - 92.4% = 7.6%
Answer: 7.6%.