Question

The sum of two numbers is 34. Their difference is 18. What are the two numbers?

Answer 1

$\left \{ {{x+y=34} \atop {x-y=18}} \right. \\+----\\\\2x=52\ \ \ \ \ |:2\\x=26\\\\26+y=34\\y=34-26\\y=8\\\\ \left \{ {{y=8} \atop {x=26}} \right.$