Sum of a finite geometric series=a(r^(n) -1)/(r -1) or sum of a finite geometric series=a(1 - r^(n))/(1 - r) the Smiths would spend a total of $2928.2 on clothing in 4 years
You can first reduce the fraction to 5 when you multiply by 3, then calculate what's in the parenthesis. So now you have 5 + 10.7 - 0.6, then just solve from left to right. Hope this helps