What must be done in order to solve for the unknown variable?

Mp model with mathematics explain how the number of text messages dario sent and the cost form an arithmetic sequence.then write an expression to find dario's text messaging bill if he sends n text messages over 250.

[15 points, algebra 2]simplify the complex fraction and find the restrictions.

When 60% of a number is added to the number the result is 192 what is the bumber