Hey there!!
Given equation :
... c(x) = 29x + 54.5
In this equation $54.50 is installation fee and this would remain as a constant. ( This value wouldn't change ).
'x' is represented as the number of months.
The total cost or c(x) is given as $344.50
Getting this into equations :
... 344.50 = 29x + 54.5
Subtracting 54.5 on both sides :
... 29x = 290
Dividing by 29 on both sides :
... x = 10
Hence, the number of months is 10.
Hope my answer helps!!
