To write an equation that represents Jill's income for a week:
1. Identify each part in the next general equation:
Initial value: b
Coefficient of change: m
The coefficient of change is the response given a one unit change. In this case she earned $9 each hour babysitting.
You give to the variable hour the letter h and multiply by 9: 9h (it means each hour she earns $9)
The initial value in this case is the amount she earns in the carpool: 40
You get the next expression for Jill's income for the week (y):