The equation would be s = 45w and she would have 360 in 8 weeks.
In order to find this, we first have to find the per week amount. To find this, we divide the amount by the number of weeks.
135/3 = 45
Now that we have this we can multiply that by the variable and set equal to the total amount.
s = 45w
Now to find the amount in 8 weeks, simply plug in the 8 to w.
s = 45w
s = 45(8)
s = 360