How do you solve #2( 9- 2y ) = 21#?

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Answer 1 · 2018-01-03T02:20:32

#y=(-3)/4#

#2(9-2y)=21#

Let's start by using the distributive property

#(2)(9)+(2)(-2y)=21#

#18 - 4y = 21#

Then subtract #color(red)(18)# from both sides

#cancel18 - 4y - cancelcolor(red)(18) = 21 - color(red)(18)#

#-4y = 3#

Then finally, divide both sides by #color(green)(-4)#

#(cancel(-4)y)/cancelcolor(green)(-4) = 3/color(green)(-4)#

#y=(-3)/4#

Answer 2 · 2018-01-03T06:50:26

Graphical Interpritation...

Graphical Approach

Since #2(9-2y) = 21 #

Both sides are equal to the same thing:

Let # x = 2(9-2y) and x = 21 #

Now sketching each of the functions...

![www.desmos.com]( useruploads.socratic.org )

Now the solution to the question is were the interesection is, hence lieing on both lines, and satifying each equation

So in this case, solving for #y#;

# color(blue)(y = -0.75 = -3/4 #