Question

what number should be subtracted from 7 upon -8 to get -13 upon 12​

Answer 1

$\sf\huge {\underline{\underline{{Solution}}}}$

Since,we don't know the number which is being substracted from 7/-8.So, let the number be 'x'

According to the question:

$\sf\implies \: \dfrac{7}{8} - x = - \dfrac{13}{12}$

$\sf\implies \: x + \dfrac{7}{8} = - \dfrac{13}{12}$

Now, on the LHS 7/8 is positive if we move to the other side it will gets substracted:

$\sf\implies \: - x = - \dfrac{13}{12} - \dfrac{7}{8}$

LCM of 12 and 8 is 24

$\sf\implies - x = \dfrac{ - 13 \times 2 - 7 \times 3}{24}$

$\sf\implies - x = \dfrac{ - 26 - 21}{24}$

$\sf\implies -x = - \dfrac{47}{24}$

$\sf = \dfrac{47}{24}$

Therefore,the number which should be substracted from 7/-8 is 47/24.

Check:

$\sf\implies - \dfrac{7}{8} - \dfrac{47}{24}$

$\sf\implies \dfrac{ - 21 - 47}{24}$

$\sf\implies - \dfrac{26}{24} = - \dfrac{13}{12}$

Answer 2

$= \frac{ - 13}{12}$