SOLUTION: How do you solve for 3/4 - 3m/4m+6 = 8? I'm really struggling with this problem, can you help me?

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: How do you solve for 3/4 - 3m/4m+6 = 8? I'm really struggling with this problem, can you help me?      Log On


   



Question 124423: How do you solve for 3/4 - 3m/4m+6 = 8?
I'm really struggling with this problem, can you help me?

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
How do you solve for 3/4 - 3m/4m+6 = 8?
:
Assume the problem is:
3%2F4 - %283m%29%2F%28%284m%2B6%29%29 = 8
:
We can see the common denominator is 4(4m+6); multiply thru by that:
4(4m+6)*3%2F4 - 4(4m+6)*%283m%29%2F%28%284m%2B6%29%29 = 4(4m+6)*8
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Cancel out the denominators and you have:
3(4m+6) - 4(3m) = 32(4m+6)
:
Multiply what is inside the brackets:
12m + 18 - 12m = 128m + 192
:
Combine the "m&m's" on the left and the numbers on the right
12m - 12m - 128m = 192 - 18
:
-128m = +174
m = 174%2F%28-128%29 = -87%2F64; reduced the fraction
:
:
This first thing one thinks when you get an answer like -87/64, is where did I go wrong?
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Well maybe that is the right answer. Take the time to substitute this for m in the original equation
:
First the numerator; 3m: 3*-87%2F64%29 = -261%2F64
Then the denominator; 4*-87%2F74 = -348%2F64 + 6 = -348%2F64+%2B+394%2F64 = +36%2F64
:
When dividing fractions invert the dividing fraction and multiply so we have:
%28-261%2F64%29+%2A+%2864%2F36%29 = -261%2F36; Canceled 64
the decimal equiv of -261%2F36 = -7.25 and decimal of 3%2F4 = .75
so we have:
.75 - (-7.25) = (minus a minus is a plus)
.75 + 7.25 = +8!!!, we are right, that is the solution
:
Did all this make sense to you, (perhaps lessen the struggle). Any questions?