$F(A,B,C) = AB+BC+AC$
$= ABC' + ABC + ABC + A'BC + AB'C + ABC$
$= ABC' + ABC + A'BC + AB'C$
$=\Sigma m(6,7,3,5)$ (m - minterm and M-maxterm))
$=\pi M(0,1,2,4)$ (proof shown below)
$F(A,B,C) = \Sigma m(3,5,6,7)$
$\implies F'(A,B,C) = \Sigma m(0,1,2,4)$
$\implies F'(A,B,C)=m_0+m_1+m_2+m_4$
$\implies (F')'(A,B,C) = (m_0+m_1+m_2+m_4)'$
$\implies F(A,B,C) = (m_0' m_1' m_2' m_4)$ (DeMorgan's law)
$\implies F(A,B,C) = (M_0 M_1 M_2 M_4)$
$\implies F(A,B,C) = \pi M(0,1 2,4)$ (Complement of a minterm is its corresponding maxterm, for example, $m_0 = A'B'C'$ and $m_0' = (A'B'C')' = A+B+C = M_0$)
Ref: http://www.cs.uiuc.edu/class/sp08/cs231/lectures/04-Kmap.pdf