Hey there!!
Fab pool service costs $35 per month, this is a variable, the number of month could change and $50 for equipment. And perfect pools cost $40( a variable ) and $35 for equipment.
Let's take the number of month as 'm'.
The question asks us to find the number of months at which both of these costs become equal.
As the question states, we will have to equate both the sums or the values.
Total cost = Cost for month + Cost for equipment.
Fab pool :
Cost per month = $35
Cost for equipment = $50
Total cost = 35 × ( the number of months ) + 50
Perfect pools :
Cost for month = $40
Cost for equipment = $35
Total cost = 40 × ( the number of months ) + 35
We have taken the number of months as 'm'.
Now, plugging in the values :
Fab pools : 35m + 50
Perfect pools : 40m + 35
Equating this :
... 35m + 50 = 40m + 35
Subtracting 35m on both sides :
... 50 = 5m + 35
Subtracting 35 on both sides:
... 15 = 5m
Dividing by 5 on both sides :
... m = 3
Hence, the number of months is 3.
Hope it helps!!