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x=-y+39 and -4/3y+136/3
x+y=39 and 3x+4y=136 -y -y -4y -4y x=38 3x= 132 /3 /3 x= 66
ok thats answer
that's not on the answer document
well, looking at my answers, the number could be 10,20,29,or30
Take the two equations, realize that you can add and subtract the two equations from each other. What I mean by that is, you can add x + y = 39 (from the first equation) to 3x + 4y = 136 (from the second) to get 4x + 5y = 175. Now some cleverness comes into play. We want to get one of the variables to cancel. To do this we can multiply either equation by a constant. Lets multiply the first equation by 4 and subtract it from the second. 4x + 4y - (3x + 4y) = 156 - 136. When you go through and cancel you boil it down to x = 20.
Oh, okay, that makes sense.
You can also verify your answer if you need to do this on a test. When you arrive at a conclusion, for instance x = 20. Plug 20 in for x in one of the equations and solve for y. From equation 1 we get 20 + y = 39, which we can see y = 19. Now plugging that into equation 2 we get 3(20) + 4(19) = 136 so our answer is correct.
Oh, thanks! I understand.
mary100 your answer is wrong there is only one answer not to. The correct answer is x=20 it is that answer because you can solve equations by graphing x+y=39 3x+4y=136 Put your answer -x -x -3x -3x in your calc and graph y=-x+39 4y=-3x+136 it than you will see 20 divide by 4 than check your y=-3/4x+34 answer
so I can do this with or without a calculator?
You can do it without a calculator but the calculator just checks it
Coming from someone with a B.S. in Math, you NEVER NEED a calculator, but they are often helpful.
Well, I came from poor schools and back then we never got to use calculators.
If you do solving equations by graphing you need a calculator but if you do elimination or substitution you totally do not need a calculator
thanks, you are great!!