Solve 3/4-12/7div12/21+4/5

$$\frac { 3 } { 4 } - \frac { 12 } { 7 } \div \frac { 12 } { 21 } + \frac { 4 } { 5 }$$

Evaluate

$$-\frac{29}{20}=-1.45$$

Solution Steps

Divide \frac{12}{7} by \frac{12}{21} by multiplying \frac{12}{7} by the reciprocal of \frac{12}{21}.

$$\frac{3}{4}-\frac{12\times 21}{7\times 12}+\frac{4}{5}$$

Cancel out 7\times 12 in both numerator and denominator.

$$\frac{3}{4}-3+\frac{4}{5}$$

Convert 3 to fraction \frac{12}{4}.

$$\frac{3}{4}-\frac{12}{4}+\frac{4}{5}$$

Since \frac{3}{4} and \frac{12}{4} have the same denominator, subtract them by subtracting their numerators.

$$\frac{3-12}{4}+\frac{4}{5}$$

Subtract 12 from 3 to get -9.

$$-\frac{9}{4}+\frac{4}{5}$$

Least common multiple of 4 and 5 is 20. Convert -\frac{9}{4} and \frac{4}{5} to fractions with denominator 20.

$$-\frac{45}{20}+\frac{16}{20}$$

Since -\frac{45}{20} and \frac{16}{20} have the same denominator, add them by adding their numerators.

$$\frac{-45+16}{20}$$

Add -45 and 16 to get -29.

$$-\frac{29}{20}$$

Factor

$$-\frac{29}{20} = -1\frac{9}{20} = -1.45$$