4  divided  by  the  difference  of  6 and  t? just the equation

That expression (not an equation) would be:

4

6-t

The probability of Jessica picking 3 consecutive red markers is: (1/6)

The probability of Jessica's first marker being red, but not picking 3 consecutive red markers is:

(3/5)−(1/6)=(13/30)

So i am bit stuck here

what i think is it shouldn't be that complex it should be as simple as chance of Jessica's first marker being red=chance of getting red 1 time i.e P(First marker being red)=(6/10) can any explain me the probability of Jessica's first marker being red=(13/30)?

Step-by-step explanation: