Question 660920
Just in case you are yet in need of understanding...
Starting with 
{{{1/4}}}(r-1)=0
Distribute the {{{1/4}}}
{{{1/4}}}r - {{{1/4}}} = 0 ***from here we can see r will equal 1***
Add {{{1/4}}} to both sides to isolate r
{{{1/4}}}r = {{{1/4}}}
Multiply both sides by 4 to further isolate r
r = {{{(1/4)*4}}}
r = 1
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