1/17-17/20

Let's calculate: $\frac{1}{17}-\frac{17}{20}$

ⓘ To add fractions, put them over the same denominator, then add the numerators. We choose $340$, the least common multiple of $17$ and $20$. Multiplying the numerator and the denominator by the same number does not change the fraction: $\frac{1}{17}-\frac{17}{20}$ = $\frac{1\times 20}{17\times 20}-\frac{17\times 17}{20\times 17}$ = $\frac{1\times 20-17\times 17}{17\times 20}$ = $\frac{20-17\times 17}{17\times 20}$

$\frac{20-17\times 17}{17\times 20}$

ⓘ Perform multiplications before additions and subtractions: $17\times 17$ = $(10+7)\times 17$ = $10\times 17+7\times 17$ = $170+119$ = $289$

ⅰ $17\times 20$ = $(10+7)\times 20$ = $10\times 20+7\times 20$ = $200+140$ = $340$

$\frac{20-289}{340}$

ⓘ The numerator and the denominator are computed before the division: $20-289$ = $-269$

▶Result:   $-\frac{269}{340}$

The numeric value of: $-\frac{269}{340}$ equals:

▷ $\approx -0.7912$