[coolboy14]

3 times the sum of k the and negative 1 equals 13.5.what is the value of k.

[morgaine300]

3 times the sum of k and negative 1 equals 13.5.

Think phrase by phase.

3 times what? The sum of k and negative 1. How do you write "sum of k and negative 1".

Then once that's written, how do you write out multiplying the whole thing by 3?

Then all that = 13.5, so that completes an equation.