In order to do this you would have to:
Simplify and Multiply x and -15 by 3:
3x-45=x+11
Subtract x from both sides:
3x-x-45=x-x+11
2x-45=11
Add 45 to both sides:
2x-45+45=11+45
2x=56
Divide 2 by both sides:
2x/2=56/2
x=28