The square of Mark's age 3 years ago is 6 times the age he will be in 9 years. What is his age now? 15
12
9

15

Step-by-step explanation:

((x-3)^2) / 6 = x + 9

Multiply both sides by 6.

6x + 54 = ((x-3)^2)

Expand.

6x + 54 = x^2 - 6x + 9

Simplify.

x^2 - 12x - 45 = 0

Solve using quadratic formula.

x = 15, -3

Since ages can only be positive, the answer is 15 years old.

a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.

answer are

step-by-step explanation: