Here there are two question I need help with them : 1. A motor car goes m yards in t seconds. If this equals v miles per hour, write the equation connecting m, t, and v. 2. The number of cents in d dimes and n nickels is given by the equation c=10d+5n. If this equation is solved for d, the result is d=(c-5n)/10. Does this give the number of dimes in cents and n nickels ? Is the equation true if solved for n ? I have some answers in my head for those questions but I want to know the idea behind them exactly, specially the second one. That's why I posted them.