Solving exponential equations with common bases

Charles is on a 8 1/2 mile bike ride. he stops for a rest after he’s gone 5 2/5 miles. how much farther does he still have to go?

Each month, a shopkeeper spends 5x + 14 dollars on rent and electricity. if he spends 3x−5 dollars on rent, how much does he spend on electricity? for which value(s) of x is the amount the shopkeeper spends on electricity less than $100? explain how you found the value(s).

Mr.zimmerman invested $25,000 in an account that draws 1.4 interest, compouneded annually. what is the total value of the account after 15 years