Question 554370
{{{3.5+f=1.2}}}
{{{3.5+f-3.5=1.2-3.5}}}
{{{cross(3.5)+f-cross(3.5)=1.2-3.5}}}
{{{f=-2.3}}}


Check
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Put the value of f in original equation
{{{3.5+(-2.3)=1.2}}}
{{{3.5-2.3=1.2}}}
{{{1.2=1.2}}}