Question

Problem page the sum of two numbers is 67 and the difference is 11 . what are the numbers?

Answer 1

Try this:
1. sum of numbers is x+y=67, the difference between them is x-y=11
2. it is possible to make up and resolve the system:
$\left \{ {{x+y=67} \atop {x-y=11}} \right. \ =\ \textgreater \ \ \left \{ {{x=39} \atop {y=28}} \right.$