Question 111203
Let numbers be {{{x}}} and {{{y}}}, and assume that {{{x > y}}}

If the sum of two numbers is {{{11}}} at most, we have:

{{{x + y = 11}}}


 If their difference is {{{21}}} we have:
 
{{{x - y = 21}}}

Now we have a system of equations:

Solve it by adding:

  {{{x + y = 11}}} 
 + {{{x - y = 21}}}.....add both equations and eliminate {{{y}}}
	
{{{x +  x + y -(y) = 11 + 21}}}

{{{2x  = 32}}}…………………divide both sides by {{{2}}}


{{{2x/2  = 32/2}}}…………………

{{{x  = 16}}}…………………

Now find {{{y}}}

{{{x + y = 11}}}……………plug in {{{x=16}}}

  {{{16 + y = 11}}}……………..move {{{16}}} to the right

  {{{ y = 11 - 16}}} 

{{{y = - 5}}}


Check:

Plug in values for {{{x}}} and {{{y}}} in previous formulas:

{{{x + y = 11}}}
{{{16 -(5) = 11}}}
{{{11 = 11}}}

another equation
{{{x - y = 21}}}
{{{x - (-5) = 21}}}
{{{16 + 5 = 21}}}
{{{21 = 21}}}