4.5 + 1.5k = 18 - 3k
Bring -3k to the other side by adding 3k to both sides
4.5 + (1.5k + 3k) = 18 + (-3k + 3k)
4.5 + 4.5k = 18 + 0
4.5 + 4.5k = 18
Bring 4.5 to the other side by subtracting it to both sides
(4.5 - 4.5) + 4.5k = 18 - 4.5
0 + 4.5k = 13.5
4.5k = 13.5
Isolate k by dividing 4.5 to both sides
4.5k / 4.5 = 13.5 / 4.5
k = 3
Hope this helped!
~Just a girl in love with Shawn Mendes