Need some help with this algebra question?

1 / 12r - 5 / 9r

1 / (3 * 4 * r) - 5 / (3 * 3 * r)

[ 1 / (3 * 4 * r) ] [ 3 / 3 ] - [ 5 / (3 * 3 * r) ] [ 4 / 4 ]

[ (1 * 3) / (3 * 3 * 4 * r) ] - [ (5 * 4) / (3 * 3 * 4 * r) ]

[ 3 / (36r) ] - [ 20 / (36r) ]

(3 - 20) / (36r)

-17 / 36r

I do not see where this is equal to something, but for setup lets try:

1st get common denominator(s) by multiplyin each set by 1 or fractions equaling 1,

36 looks like the least or lowest for 12 and 9, so

1/12r*(3/3) - 5/9r *(4/4) =?

then 3/36r -20/36r =?

so, (3 -20)/36r simplifies to or = -17/36r

I'm assuming you want to simplify... To do so:

Find a common denominator (use greatest common factor)

1/(12r)-5/(9r)

= 9/(108r)-60/(108r)

Subtract

=-51/(108r)

Simplify

-17/(36r)

-1 19/36r or -17/36r