Answer:
35
Step-by-step explanation:
Use the combination formula:
[tex]C(n,r)=\frac{n!}{r!(n-r)!}[/tex]
Substitute known values:
[tex]C(7,3)=\frac{7!}{3!(7-3)!}=35[/tex]
We don't use the permutation formula since the order of the drawn marbles does not matter.