Question 384111
I did it two ways because your problem setup was unclear. 
Neither ways gets your answer. 
Check your problems setup.
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{{{(x +1)/ 12 = 3/20}}}
{{{x+1=36/20}}}
{{{x+1=9/5}}}
{{{x=9/5-5/5}}}
{{{highlight(x=4/5)}}}
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{{{x+1/12=3/20}}}
{{{x=3/20-1/12}}}
{{{x=36/240-20/240}}}
{{{x=16/240}}}
{{{highlight_green(x=1/15)}}}