A girl spends 76% 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)?

Let the income of girl is 100

Expenditure is 76% of income 

i.e, $$\frac{76}{100}\times\ 100$$

= 76

Saving = Income - expenditure

100 - 76 = 24

According to question, 

income is increased by 18%

Increased income = $$\frac{18}{100}\times\ 100\ +\ 100=118$$

Expenditure is increased by 25% 

increased expenditure = $$\frac{25}{100}\times\ 76\ +\ 76=95$$

New saving = 118 - 95 = 23

% decrease in saving = $$\frac{\left(24-23\right)}{24}\times\ 100$$

i.e; $$4.16\ \simeq\ 4.2\ \%$$

Hence, Option B is correct.