A girl spends 80% of her income. If her income increases by 18% and her expenditure increases by 25%, then what is the percentage increase or decrease in her savings (correct to one decimal place)?

Given, 

A girl spend 80% of its income.

Let the income of the girl is 100x.

Expenditure is 80% of income = $$\frac{80}{100}\times\ 100x=80x$$

Saving = income - expenditure 

= `100x - 80x = 20x

According to question, 

Income is increased by 18% = 100x + $$\frac{18}{100}\times\ 100x=118x$$

Increase in expenditure is 25% = 80x + $$\frac{25}{100}\times\ 80x=100x$$

New saving = 118x - 100x = 18x 

Required Decreased % = $$\frac{\left(20x-18x\right)}{20x}\times\ 100=10\%$$

Hence, Option B is correct.