The difference between 5 times a number and 3 is 12. What is the number?

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

Which of the following represents the range of the graph of f(x) below

Find the domain of the following expression: 1/(√x)-2