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what is 8r+40-5(3r+7) ? 
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Re: what is 8r+40-5(3r+7) ?
by little_dragon on Wed Jul 06, 2011 10:50 pm
kpw2010 wrote:what is 8r+40-5(3r+7) ????
its a math expression. R U supposed to do something w/ it?
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Re: what is 8r+40-5(3r+7) ?
by raj_patel on Thu Jul 07, 2011 4:01 pm
You must first know whether you are simplifying the expression or solving for a numeric value. In either case, combining like terms is necessary.
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Re: what is 8r+40-5(3r+7) ? 
by ambidex on Wed Aug 10, 2011 7:46 pm
If that's the exact question, then you're supposed to evaluate it.
If the question were 8 + 40 - 5(3 + 7), you'd know what to do, because all you have is numbers. You'd follow PEMDAS, do 3 + 7, then multiply by 5, then subtract your answer from 40 and then add 8. That would look like: 8 + 40 - 5 (11) = 8 + 40 - 55 = 8 -15 = -7.
When you don't just have numbers, like in the problem you've specified, you have to know how to deal with variables. "r" is a variable in your problem. What you're going to do is find all of the "r" numbers and do "math" with those numbers. This what is called "combining like terms." However, you'll find that "3r" is kind of stuck so what you need to do is use the distributive property to get it "unstuck". Here's what that'll look like: 8r + 40 - 5*3r + 5*7. Keep going: 8r + 40 - 15r + 35. Now you just have two r numbers and two normal numbers. Let's rearrange them: 8r - 15r + 40 + 35.
This isn't the final answer, but I hope you can find your final answer from here!
If the question were 8 + 40 - 5(3 + 7), you'd know what to do, because all you have is numbers. You'd follow PEMDAS, do 3 + 7, then multiply by 5, then subtract your answer from 40 and then add 8. That would look like: 8 + 40 - 5 (11) = 8 + 40 - 55 = 8 -15 = -7.
When you don't just have numbers, like in the problem you've specified, you have to know how to deal with variables. "r" is a variable in your problem. What you're going to do is find all of the "r" numbers and do "math" with those numbers. This what is called "combining like terms." However, you'll find that "3r" is kind of stuck so what you need to do is use the distributive property to get it "unstuck". Here's what that'll look like: 8r + 40 - 5*3r + 5*7. Keep going: 8r + 40 - 15r + 35. Now you just have two r numbers and two normal numbers. Let's rearrange them: 8r - 15r + 40 + 35.
This isn't the final answer, but I hope you can find your final answer from here!
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