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put this solution on YOUR website!Let a the first number and b the second one
When the first of two numbers is added to twice the second the result is 21,
then a+2b=21
when the second number is added to twice the first the result is 18.
then 2a+b =18
a+2b=21
2a+b =18
doing first eq by -2 we have
-2a+-4b=-42
2a+b=18
adding both eq
-3b=-24
b=8 and a+2(8)=21
then a+16=21
a=5
Solution: a=5 and b=8