To add unlike denominator you have to make the denominator like , in order to subract them .
- Find the LCM of 7x and 3x
= 21
- Multiply both denominator so that there LCM comes as 21 , and multiply same number with numerator .
[tex] - \frac{4 \red{ \times 3}}{7x \red{ \times 3}} - \frac{5 \red{ \times 7}}{3x \red{ \times 7}} \\ \\ \implies \: (making \: denominator \: common) \\ \\ \frac{- 12 - 35}{21x } [/tex]
[tex] \boxed {\purple{ans = \frac{23}{21x} }}[/tex]
