Answer :

a386
Combine like terms-- you can combine the k's:
[tex]4k-1.5k=2.5k[/tex]

Now you have:
[tex]2.5k=50[/tex]

Simply divide both sides by 2.5 to find the value of k:
[tex]\frac{2.5k}{2.5}=\frac{50}{2.5}\\\\k=20[/tex]