1/8-13/20

Let's evaluate: $\frac{1}{8}-\frac{13}{20}$

ⓘ To add fractions, put them over the same denominator, then add the numerators. We choose $40$, the least common multiple of $8$ and $20$. Multiplying the numerator and the denominator by the same number does not change the fraction: $\frac{1}{8}-\frac{13}{20}$ = $\frac{1\times 5}{8\times 5}-\frac{13\times 2}{20\times 2}$ = $\frac{1\times 5-13\times 2}{8\times 5}$ = $\frac{5-13\times 2}{8\times 5}$

$\frac{5-13\times 2}{8\times 5}$

ⓘ Multiplications are done before additions and subtractions: $13\times 2$ = $(10+3)\times 2$ = $10\times 2+3\times 2$ = $20+6$ = $26$

ⅰ $8\times 5$ = $40$

$\frac{5-26}{40}$

ⓘ Calculate the numerator and denominator before dividing: $5-26$ = $-21$

▶Result:   $-\frac{21}{40}$

The numeric value of: $-\frac{21}{40}$ is:

▷ $-0.525$