Question

3/4 din 120, 4/5 din 20,
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Answer 1

3/4 din 120 =$\frac{3*120}{4}$=90

4/5 din 20=$\frac{20*4}{5\\}$=16

Answer 2

$\frac{3}{4}\cdot \:120 =\frac{3}{4}\cdot \frac{120}{1} =\frac{3\cdot \:120}{4\cdot \:1} =\frac{3\cdot \:120}{4} =3\cdot \:30 = 90$

$\frac{4}{5} \cdot 20 = \frac{4}{5}\cdot \frac{20}{1} =\frac{4\cdot \:20}{5\cdot \:1} =\frac{4\cdot \:20}{5} =4\cdot \:4=16$