Originally Posted by
Jhevon what you have is $\displaystyle 7 \sum_{k = 1}^{48}k + \sum_{k = 1}^{48}5$
Now recall that $\displaystyle \sum_{i = 1}^ni = \frac {n(n + 1)}2$ and $\displaystyle \sum_{i = 1}^nc = cn$ where $\displaystyle c$ is a constant.
Can you finish up?