# How do you convert 7.5 x 10^4 j into kilojoules?

The prefix $k$ (kilo) means 1000.
$7.5 \cdot {10}^{4} J = 7.5 \cdot 10000 J = 75000 J$
$75 \cancel{000} \cancel{J} \cdot \frac{1 k J}{1 \cancel{000} \cancel{J}} = 75 k J$