Question

Help, 3+7x=12, what is x?

Answer 1

So just your normal equation. 
We need to isolate x alone. 
First lets write out our equation 
3 +7x = 12 

Lets do this step by step. 

first subtract 3 from both sides. 
3 + 7x = 12  
-3        = -3  it cancels out on the left side and we solve on the right side. 
*************
7x = 9 

second we divide both sides by 7 
7x = 9 
÷7 = 7      we got the x alone and we just write 9/7 as our answer. 

x = 9/7 

Or as a decimal. 
9/7 could be 1.28571428571429

Either will work. 
x = 9/7 
or 
x = 1.28571428571429

Have a nice day. :)