Answer:
[tex]\huge\boxed{\sf \frac{x+3}{x-3}}[/tex]
Step-by-step explanation:
[tex]\displaystyle = \frac{x+7}{x^2+4x-21} \div \frac{x+5}{x^2+8x+15} \\\\Apply \ mid-term \ break\\\\= \frac{x+7}{x^2 +7x-3x-21} \div \frac{x+5}{x^2 +3x+5x+15} \\\\= \frac{x+7}{x(x+7)-3(x+7)} \div \frac{x+5}{x(x+3)+5(x+3)} \\\\Taking \ (x+3) \ and \ (x+7) \ common\\\\= \frac{x+7}{(x-3)(x+7)} \div \frac{x+5}{(x+3)(x+5)} \\\\= \frac{1}{x-3} \div \frac{1}{x+3} \\\\= \frac{1}{x-3} * (x+3)\\\\= \frac{x+3}{x-3} \\\\\rule[225]{225}{2}[/tex]
Hope this helped!
~AH1807
