d=dante's cards number
a=anna's cards number
d=60
this (d) is at least (smallest is, aka greater than or equal to or >) 6 more than (+6) 3 times as many as anna (3 times a or 3a)
d>6+3a
d=60
60>6+3a
subtract 6 from both sides
54>3a
divide both sides by 3
18>a
anna has at least 18 cards
