Question 1043661
LET {{{P}}} be the principal
interest added is
 {{{5/100*P}}} 
{{{p+5/100*p}}}=126
solving for p
{{{p+5/100*p}}}=126
{{{p+0.05*p}}}=126
{{{1.05*p}}}=126
{{{p=120}}}

Check
{{{120+0.05*120}}}=126 is indeed true