Question

By what number should we multiply −15 by 20 so that the product may be −5 by 7

Answer 1

$let \: the \: number \: be \: x \\ \frac{ - 15}{20} \times x = \frac{ - 5}{7} \\ x = \frac{20}{21}$
hope you get the answer

Answer 2

Let the no. to be multiply be x
then
x×-15/20=-5/7
x=20/21