Which of the following situations represents a proportional relationship?
a. a cheeseburger is $7.95 plus $ 1.00 for each additional topping.
b. a pool fills at a rate of 90 gallons per hour.
c. a health club charges a $40.00 membership fee plus $25.00 per month
d. a bank account begins with $350.00 and gains $30.00 per month.

Girardo is using the model below to solve the equation . girardo uses the following steps: step 1 add 4 negative x-tiles to both sides step 2 add 1 negative unit tile to both sides step 3 the solution is which step could be adjusted so that gerardo's final step results in a positive x-value? in step 1, he should have added 4 positive x-tiles to both sides. in step 1, he should have added 3 negative x-tiles to both sides. in step 2, he should have added 4 negative unit tiles to both sides. in step 2, he should have added 1 positive unit tile to both sides.