Answer:
-3
Step-by-step explanation:
The given expression is:
[tex]\frac{\frac{a-3}{7} }{\frac{3-a}{21} }[/tex]
We can rewrite this as:
[tex]\frac{a-3}{7}\div \frac{3-a}{21}[/tex]
[tex]\frac{a-3}{7}\times \frac{21}{3-a}[/tex]
Factor -1 out of the first numerator:
[tex]\frac{-(3-a)}{7}\times \frac{21}{3-a}[/tex]
Cancel out the common factors;
[tex]\frac{-1}{1}\times \frac{3}{1}=-3[/tex]
