You need to find "k", by isolating/getting "k" by itself in the equation
16.3k + 19.2 + 7.5k = -64.1 First combine like terms, 16.3k and 7.5k
23.8k + 19.2 = -64.1 Subtract 19.2 on both sides
23.8k = -83.3 Divide 23.8 on both sides to get "k" by itself
k = - 3.5