一條難度十分高的英文百分數題

The equation should be

X (1+10%) (1-10%) = X

The question means increment by 10% is X (1+10%) <= New amount
Then the increased amount decrease by 10%, i.e. the new amount times (1-10%)

So, it should be X (110%) (90%) =X
Then, 99% X = X
X seems equal to "0"

Peter's calculation is wrong. The right method is as follows:

new value of X = (1+10%) (1-10%) X
= (1.1) (0.9) X
= 0.99X

Therefore, new value of X should become less.

x is increased by 10% ------>(1+10%)x = 1.1x

then decreased by 10%----> (1-10%)* 1.1x
----->0.99x

When a number x is increased by 10%, it becomes 1.1x
And then decreased by 10%, it becomes 0.99x
The value of x has been decreased by 1%
His mistake is that the formula should be
x (1+10%)(1-10%) instead of x(1 + 10% - 10%)

100% + 10% = 110%
110% * 0.9 = 99%

X went down from 100% to 99%