SOLUTION: Please help me to solve this equation/problem: 21-y=2y I know that y=7 but my teacher said I have to show working and I don't know how to do this.

Question 772395: Please help me to solve this equation/problem: 21-y=2y
I know that y=7 but my teacher said I have to show working and I don't know how to do this.

Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!
You want all terms of y on one side of the equal sign and all constants on the other side of the equal sign. The simplest way is like this:

Equation given is the same as 21+(-y)=2y

Add the additive inverse of (-y) to both sides.
Combine like-terms of y.
Multiply both sides by the multiplicative inverse of the factor attached to the y term.
Simplify if needed.
Finished.
RELATED QUESTIONS
Please help me solve this equation... PROBLEM: -3(2y-8)-y=-2(y-4) After working through (answered by math-vortex)

I am trying to solve a linear equation with three variables and I am stuck on this... (answered by KMST)

-3xyz(squared) x=-4 y=-2 z=1\2 okay when i put this equation in my TI calculator i... (answered by nerdybill)

The problem is as follows- Solve by useing Substitution: x+y=20} 5x+10y=200} I made... (answered by tishy)

Please help me with this problem. I have similar problems in my homework but it does not... (answered by solver91311,edjones)

Hi, this is more of a calculus problem and I didn't really know where to go for help.... (answered by jim_thompson5910)

(-1,5);m=-4/7 I have asked for help but still don't know how to get to my answer. I... (answered by Alan3354)

{{{(x+3)^2=-8(y-5)}}}. How do I find P for this problem? I know that its from the... (answered by lwsshak3)

Okay, I have this problem I got wrong on my test but I thought I got it right. (answered by josgarithmetic)