Question 642694
You made a mistake in <font color="red">red</font> below


12+3<font color="red">-5</font>=10


when it *should* be


12+3-10 = 5


which becomes 5/2


So 


12/2x+3/2x-10/2x=15


5/2x=15


5x = 15*2


5x =  30


x = 30/5


x = <font color="red">6</font>


So the solution is x = <font color="red">6</font>