Question 479997
Let x and y are numbers
Half of the sum is {{{(x+y)/2}}} is 20, so {{{(x+y)/2=20}}}
Three times their difference {{{3(x-y)=18}}}
The system of the equations
{{{system((x+y)/2=20, 3(x-y)=18)}}} multiply the first equation by 2, divide the second equation by 3
{{{system(x+y=40, x-y=6)}}} add the second equation to the first
{{{2x=46}}}
{{{x=46/2}}}
{{{x=23}}} is the first number
{{{23+y=40}}}
{{{y=40-23}}}
{{{y=17}}} is the second number