Also the slant form makes it easier for the eye to examine the denominators to see whether reductions are necessary.
He then took the liberty of taking the mean of both numerators and denominators, giving 355/113.
Reduce the fractions to like denominators, add their numerators and write the denominator under the result.
Reduce the fractions to like denominators, subtract the numerators and write the denominators under the result.
Multiply the numerators together for a new numerator and the denominators together for a new denominator.
The numerator of the third is the sum of the numerators of the first and second, its denominator, the sum of the two denominators.