The sum of two numbers is 21. Twice the first number less than the second equals 6. What are the two numbers?

2
by gaby1234567890
ASAP!!
wait let me do the solution

2016-01-27T15:38:50+08:00

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12 and 9 is the answer
• Brainly User
2016-01-28T08:33:13+08:00

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Equation 1)    x + y = 21
y = 21 - x

Equation 2)  2x - y = 6

Solve the system by substitution:
Substitute  21-x for y in Equation 2:

2x - (21-x) = 6
2x + (-21 + x) = 6      (Change the sign of each term of  the subtrahend,    then add/combine like terms)

2x + x - 21 = 6
3x = 6 + 21
3x/3 = 27/3
x = 9

Substitute 9 for x:
First number: x = 9
Second number: 21-9 = 12

ANSWER:  The numbers are 9 (first number) and 12 (second number).

Check:
9 + 12 = 21
21 = 21    (True)

2(9) - 12 = 6
18 - 12 = 6
6 = 6  (True)