Question 210015
Let x = the number to be added.


{{{ (3+x)/10 = 4/5}}}


Remember that if {{{a/b= c/d}}} then {{{ad=bc}}}


So, {{{ (3+x)/10 = 4/5}}} means that {{{5(3+x)= 4*10}}}


15+5x = 40
5x=40-15
5x=25
x=5


Check:  Add 5 to the numerator of 3 which gives you 8.  {{{8/10= 4/5}}}.


It checks!!!


R^2