Hi!
The probability that you are dealt a card with number from 4 to 9, since there are four 4s, four 5s, four 6s, four 7s, four 8s and four 9s, which sums up to 4 + 4 + 4 + 4 + 4 + 4 = 24, and there are 52 cards in the deck: P(4-9) = 24/52
The probability that you are not dealt a card with number from 4 to 9 is calculated like this:
P = 1 - P(4-9)
P = 1 - 24/52 = 52/52 - 24/52 = 28/52
P = 28/52 = 14/26 = 7/13
Hope this helps!