What does it mean to say that two variables are directly proportional?

In the figure shown below, m < 40 and ab =8. which equation could be used to find x?

Dakota earned $7.50 in interest in account a and $18.75 in interest in account b after 15 months. if the simple interest rate is 4% for account a and 5% for account b, which account has the greater principal? explain. to make it a little easier, there is an image. good luck!

Identify one charcteristic of exponential growth