Find the numerical value of k:
-2.35=[(k-100)/15]
Solve this like you would any algebraic equation.
-2.35 = (k - 100)/15
First multiply both sides by 15 to get rid of the denominator on the right hand side (whatever operation you do to one side of an equation you must do to the other side as well).
15 * -2.35 = k - 100
-35.25 = k - 100
Add 100 to both sides to get k by itself. When you do that operation, you will find the value of k.
I hope this helps.