Answer:
d. Variable ratio
Step-by-step explanation:
We are asked to determine that gambling at a slot machine is an example of which reinforcement schedule.
Let us see our given choices one by one.
a. Fixed ratio
We know that in fixed ratio schedule, reinforcement is delivered after the completion of a number of responses. An example of fixed ratio is a reward to every 6th response.
b. Fixed interval
We know that in fixed interval schedule the first response is rewarded only after a specified amount of time has elapsed. An example of fixed interval schedule is weekly paycheck.
c. Variable interval
We know that in variable interval schedule, the reinforcement is delivered at changing and unpredictable intervals of time.
d. Variable ratio
In variable ratio schedule, a response is reinforced after an unpredictable number of responses. Gambling and lottery are examples of variable ratio.
Therefore, option 'd' is the correct choice.
Answer:

Step-by-step explanation:
Set up the equation:
Since C(t) gives the number of cars purchased in the t-th year after 1998, then make the number of cars equal to 15 000 and solve for t - the year:
20t^2 = 15000
t^2 = 750
t = 
The year will be simply 1998 + 5 \sqrt{30}
Answer:
18
Step-by-step explanation:
6 + 6 + 6 = 18
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Factor 3x^2 - 12x + 3
3x^2 - 12x + 3
answer is 3(x^2 - 4x + 1)