Simplify 1/(3x^3)-4/5

$\frac{1}{3 x^{3}} - \frac{4}{5}$

To write $\frac{1}{3 x^{3}}$ as a fraction with a common denominator, multiply by $\frac{5}{5}$ .

$\frac{1}{3 x^{3}} \cdot \frac{5}{5} - \frac{4}{5}$

To write $- \frac{4}{5}$ as a fraction with a common denominator, multiply by $\frac{3 x^{3}}{3 x^{3}}$ .

$\frac{1}{3 x^{3}} \cdot \frac{5}{5} - \frac{4}{5} \cdot \frac{3 x^{3}}{3 x^{3}}$

Write each expression with a common denominator of $15 x^{3}$ , by multiplying each by an appropriate factor of $1$ .

Multiply $\frac{1}{3 x^{3}}$ by $\frac{5}{5}$ .

$\frac{5}{3 x^{3} \cdot 5} - \frac{4}{5} \cdot \frac{3 x^{3}}{3 x^{3}}$

Multiply $5$ by $3$ .

$\frac{5}{15 x^{3}} - \frac{4}{5} \cdot \frac{3 x^{3}}{3 x^{3}}$

Multiply $\frac{4}{5}$ by $\frac{3 x^{3}}{3 x^{3}}$ .

$\frac{5}{15 x^{3}} - \frac{4 (3 x^{3})}{5 (3 x^{3})}$

Multiply $3$ by $5$ .

$\frac{5}{15 x^{3}} - \frac{4 (3 x^{3})}{15 x^{3}}$

Combine the numerators over the common denominator.

$\frac{5 - 4 (3 x^{3})}{15 x^{3}}$

Multiply $- 4$ by $3$ .

$\frac{5 - 12 x^{3}}{15 x^{3}}$