Question 314861
The two numbers are A and B.
1.{{{A+B=84}}}
2.{{{A=3B}}}
Substitute eq. 2 directly into eq. 1 and solve for B.
{{{A+B=84}}}
{{{(3B)+B=84}}}
{{{4B=84}}}
{{{highlight_green( B=21)}}}
Then from eq. 2,
{{{A=3B=3(21)}}}
{{{highlight_green( A=63)}}}
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The two numbers are 21 and 63.