<p>Ok, this problem is pretty easy, and I get the final answer, but I can't seem to break it down all that well. Would someone mind doing this problem step-by-step?</p>
<p>If 2x+4y=9, what is the value of x+2y?</p>
<p>Final answer should be 4.5. Thanks.</p>
<p>Let 2x+4y=z
then z/2= x+2y</p>
<p>we want to find the value of z/2</p>
<p>since we know z=9, z/2=4.5</p>
<p>Just divide each term by 2. </p>
<p>2x + 4y = 9</p>
<p>x + 2y = 9/2</p>
<p>Or you could plug in. Say y=2 and x=.5</p>
<p>That gives you 1+8=9, which checks out in the question. Then you get .5 +4 which equals 4.5</p>
<p>Picking numbers - </p>
<p>Pick values for x and y that make the equation 2x+4y=9 true.</p>
<p>(such as 2.5 for x and 1 for y)</p>
<p>2<em>2.5 + 4</em>1 = 9 , so these work</p>
<p>then, just transfer these values over the the algebraic term in question- </p>
<p>x + 2y ----> 2.5 + 2*2 = 4.5 or 9/2</p>
<p>^
Awkward. lol</p>
<p>Without question, what they intend you to do is to notice that the expression they’re asking the value of, (x+2y), is half the expression that they told you the value of, (2x+4y). So you need to divide the value of (2x+4y) by 2. 9/2 = 4.5.</p>
<p>The SAT uses variations on this theme a lot. If you know the value of some expression, find the value of a multiple of that expression. Sometimes you can find the values of the individual variables (and I bet sometimes you can’t), but if you you do that, you’re going way out of your way and burning a lot of time that you really want for the questions that are supposed to be harder.</p>
<p>Remember that it is an EQUATION - each side has to equal the other. Whatever operation you perform on one side also has to be performed on the other side.</p>
<p>I picture a scale that is balanced perfectly. If I change the quantity on one side, I have to change the quantity on the other side by exactly the same amount, or the scale will tip out of balance.</p>