From Förberedande kurs i matematik 1

The first step is to expand the fractions so that they have a common denominator,

\displaystyle \frac{8\centerdot 4\centerdot 3}{7\centerdot 4\centerdot 3}+\frac{3\centerdot 7\centerdot 3}{4\centerdot 7\centerdot 3}-\frac{4\centerdot 7\centerdot 4}{3\centerdot 7\centerdot 4}=\frac{96}{84}+\frac{63}{84}-\frac{112}{84}

After that, the expression can be calculated by adding and subtracting the numerators

\displaystyle \frac{96}{84}+\frac{63}{84}-\frac{112}{84}=\frac{96+63-112}{84}=\frac{47}{84}