Hi!
a: <em>F </em><em>n </em><em>G </em>=(Intersection) {4,6,8,10}
b: <em>F </em><em>n </em><em>H </em>={empty set}
Because there is no common element between the elements of set F and the elements of set H.
Note: It may not be very clear as I don't speak English.
God work!