Answer
465
Work Step by Step
$\sum ^{15}_{j=1}\left( 5j-9\right) =5\sum ^{15}_{j=1}j-\sum ^{15}_{j=1}9=5\times \dfrac {n\left( n+1\right) }{2}-9\times n=5\times \dfrac {15\times \left( 15+1\right) }{2}-9\times 15=5\times 15\times 8-9\times 15=465$