Can someone please help

Answer:
12x+3x=15+6
15x=21
divide both sides by 15
x=7/5
Answer:
hey well use transposition method in this
so 12x-15=6-3x
so.12x+3x-15=6 (we transposed-3 to other side so it became +3)
15x-15=6
15x=6+15
15x=21
X=21/15
X= 1.4
I think I'm correct but if wrong pls don't report me just correct me so I can learn