Answer:
The answer is "35"
Step-by-step explanation:
[tex]\to n=7\\\\\to r=3\\\\Formula:\\\\\to {}^{n}C_{r}= \binom{n}{r}= \frac{n!}{r!(n-r)!}\\\\[/tex]
[tex]\to {}^{7}C_{3}= \binom{7}{3}= \frac{7!}{3!(7-3)!}\\\\[/tex]
[tex]= \frac{7\times 6 \times 5 \times 4!}{3! \times 4!}\\\\= \frac{7\times 6 \times 5 }{3!}\\\\= \frac{7\times 6 \times 5 }{3\times 2 \times 1}\\\\ = 7 \times 5 \\\\= 35[/tex]