Answer:
y = 150x + 400
Step-by-step explanation:
Slope intercept form is : y = mx + b
B is the y intercept, you can also think of it like a starting value, in this case Susan starts with $400 dollars
M is the slope, you can also think of it like a value that is consistently changing over time, in this case Susan saves(or earns) $150 each month.
If you want to figure how much money she will have in a certain number of months, plug the number of months (x), into the x in y = 150x + 400.