How to find standard deviation when know probabilities and mean

Carl wants to buy a television that cost $500 including taxes. to pay for television he will use a payment plan that requires him to make a down payment of $125 and then pay $70.50 each month for six months what is the percent increase from the original cast of the television to the cost of the television using a payment plan.

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?

The graph of y=x3 is transformed as shown in the graph below. which equation represents the transformed function?