Question 124423
How do you solve for 3/4 - 3m/4m+6 = 8? 
:
Assume the problem is:
{{{3/4}}} - {{{(3m)/((4m+6))}}} = 8
:
We can see the common denominator is 4(4m+6); multiply thru by that:
4(4m+6)*{{{3/4}}} - 4(4m+6)*{{{(3m)/((4m+6))}}} = 4(4m+6)*8
:
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/(-128)}}} = {{{-87/64}}}; reduced the fraction
:
:
This first thing one thinks when you get an answer like -87/64, is where did I go wrong?
:
Well maybe that is the right answer. Take the time to substitute this for m in the original equation
:
First the numerator; 3m: 3*{{{-87/64)}}} = {{{-261/64}}}
Then the denominator; 4*{{{-87/74}}} = {{{-348/64}}} + 6 = {{{-348/64 + 394/64}}} = +{{{36/64}}}
:
When dividing fractions invert the dividing fraction and multiply so we have:
{{{(-261/64) * (64/36)}}} = {{{-261/36}}}; Canceled 64
the decimal equiv of {{{-261/36}}} = -7.25 and decimal of {{{3/4}}} = .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?