Answer: She had $70 at the beginning.
Step-by-step explanation:
Lets represent this situation as an equation where we will use y to represent the amount of money left and x for the number of days.
Using the formula y = mx + b , we can say b will be the amount in 0 days because its the y intercept and the y intercept is when x is 0.
m will be the rate of change and the rate of change will be -5 per day because he is spending.
In 9 days, he had $25 left and we can also represent that by the point (9,25)
Now input the values for x and y into the formula with the slope and solve for b.
y = mx + b
25 = -5(9) + b
25 = - 45 + b
+45 +45
b = 70
This means she started with $70.
