Question 108858
The expression "Two numbers have a sum of 39" is written as


{{{x+y=39}}}


and "Their difference is 11" is written as


{{{x-y=11}}}


So we get the system 



{{{x+y=39}}}
{{{x-y=11}}}


*[invoke solving_linear_system_by_substitution 1, 1, 39, 1, -1, 11]