Question

The sum of two numbers is 92.Their difference is 20

Answer 1

Sum means + difference is division 
 x + y = 92 
 x - y = 20 

2x = 92 +20 
2x = 112 
x = 56 

x + y =92 
56 + y = 92 
y = 36 
'
answer 36 and 56

Answer 2

$\begin{cases} x+y=92 \\x-y=20 \end{cases}\\+-------\\2x=112\ \ | \ divide \ both \ sides\ by\ 2\\x=56\\\\x+y=92\\56+y=92\\y=92-56\\y= 36\\\\\begin{cases} x=56 \\y=36 \end{cases}\\\\Answer:\ \ Therefore, \ the \ two \ numbers \ are \ 36 \ and \ 56$