This is an example of a random variable that follows Bernoulli distribution.
Whenever you perform [tex]n[/tex] experiments, with probability [tex]p[/tex] of success, the provability of havin [tex]k[/tex]successes is
[tex]P(X=k)=\displaystyle\binom{n}{k}p^k(1-p)^{n-k}[/tex]
In this case, you have [tex]n=3[/tex] (you choose a sample of 3 candidates), [tex]p=0.3[/tex] (30% of candidates have a degree in economics) and we want [tex]k[/tex] to be at least one.
One way to solve this is to consider that
[tex]P(X\geq 1)=P(X=1)+P(X=2)+P(X=3)[/tex]
But it is much quicker to observe that
[tex]P(X\geq 1)=1-P(X<1)=1-P(X=0)[/tex]
And we have
[tex]P(X=0)=\displaystyle\binom{3}{0}0.3^0\cdot 0.7^{3}=1\cdot 1\cdot 0.7^3[/tex]
So, the probability that at least one of them has a degree in economics is
[tex]1-0.7^3 = 0.657[/tex]
