Systems of Equations with Three Variables word problem!!! HELP!! Super challanging.

SAkulonis

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I need help with this problem! Please show work, you must use THREE equations and THREE variables, a,b, and c. Where A= ones place, B= tens place C= Hundreds place. Its a year, so the Thousandths place is 1. Find The year in which the first U.S transcontinental railroad was completed. The following are some facts about the number. The sum of the digits (a+b+c=24 * this is the first equation) is equal to 24. The ones digit is 1 more than the hundreds digit (a=c+1*is the second equation). Both the tens and the ones digits are multiples of 3. ******** Now the ANSWER is 1869. I know this because I looked it up (cheated) and it worked. BUT my teacher is not going to accept the guess and check method, I need real work. I cant figure out the third equation to use. we'll see what you get!
 
Further help....

Try again: a+b+c = 23, NOT 24.

Come back if you need further help.....but SHOW your work....
Well, yes, I do need further help!! And no, it's not 23. I said the sum of the digits, which yes I just made a typo, it's 1 + a+ b+c= 24. The sum of the digits, 1+8+6+9=24. I only know what the answer is because I googled it, I need to know how to get there, that's why I posted the question. I don't have work and I need work. I don't know the third equation, and I don't know how to find it! Please help!
 
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THREE variables, a, b, and c.

Where A= ones place, B= tens place C= Hundreds place.

Don't mix upper- and lower-case symbols; use one version or the other (not both).



a+b+c=24*

a=c+1*

What's up with the asterisks? When typing algebraic expressions, an asterisk means multiplication.

:idea: Equations are easier to read, when typed each on their own line (double-spaced). When equations are imbedded within paragraphs of text, they are not easy to read.



Both the tens and the ones digits are multiples of 3. ********

Ok. ******** ;)

If you add the first two equations, you can get a third equation.

a + (1/2)b = 12

There are only four digits which are multiples of 3. The factor of 1/2 in the third equation tells us that b must be even.

HINT: There is only one even digit (not counting 0) which is a multiple of 3.

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