Step 1: Calculate the total fraction of salary spent on food and rent. $$ \text{Fraction spent on food and rent} = \frac{1}{3} + \frac{2}{7} $$ To add these fractions, find a common denominator, which is $3 \times 7 = 21$. $$ \frac{1}{3} + \frac{2}{7} = \frac{1 \times 7}{3 \times 7} + \frac{2 \times 3}{7 \times 3} = \frac{7}{21} + \frac{6}{21} = \frac{7+6}{21} = \frac{13}{21} $$ Step 2: Calculate the remainder of the salary after spending on food and rent. $$ \text{Remainder} = 1 - \text{Fraction spent on food and rent} $$ $$ \text{Remainder} = 1 - \frac{13}{21} = \frac{21}{21} - \frac{13}{21} = \frac{21-13}{21} = \frac{8}{21} $$ Step 3: Calculate the fraction of the remainder spent on transport. The employee uses $\frac{1}{4}$ of the remainder on transport. $$ \text{Fraction spent on transport} = \frac{1}{4} \times \text{Remainder} $$ $$ \text{Fraction spent on transport} = \frac{1}{4} \times \frac{8}{21} = \frac{1 \times 8}{4 \times 21} = \frac{8}{84} = \frac{2}{21} $$ Step 4: Calculate the fraction of salary saved. The employee saves the rest of the remainder after transport. If $\frac{1}{4}$ of the remainder is spent on transport, then $1 - \frac{1}{4} = \frac{3}{4}$ of the remainder is saved. $$ \text{Fraction saved} = \frac{3}{4} \times \text{Remainder} $$ $$ \text{Fraction saved} = \frac{3}{4} \times \frac{8}{21} = \frac{3 \times 8}{4 \times 21} = \frac{24}{84} $$ Simplify the fraction by dividing the numerator and denominator by their greatest common divisor, which is 12. $$ \frac{24 \div 12}{84 \div 12} = \frac{2}{7} $$ The fraction of his salary he saves is $\boxed{\frac{2}{7}}$. That's 2 down. 3 left today — send the next one.