Question

Calculati
(-1/5+3/10):21/20

Answer 1

= (-1/5+3/10)÷21/20
= (-2/10+3/10)
= 1/10÷21/20
= 1/10×20/21
= 20/21
= 2/21

Answer 2

$( - \frac{1}{5} + \frac{3}{10}) \div \frac{21}{20} = \frac{1}{10} \div \frac{21}{20} = \frac{1}{10} \times \frac{20}{21} = \frac{1 \times 20}{10 \times 21} = \frac{20}{210} = \frac{2}{21}$