A first number plus twice a second number is 14. Twice the first number plus the second totals 40. F | MathCelebrity Forum

A first number plus twice a second number is 14. Twice the first number plus the second totals 40. F

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A first number plus twice a second number is 14. Twice the first number plus the second totals 40. Find the numbers.

Givens and assumptions:
  • Let the first number be x.
  • Let the second number be y.
  • Twice means multiply by 2
  • The phrases is and totals mean equal to

We're given two equations:
  1. x + 2y = 14
  2. 2x + y = 40
To solve this system, we can take a shortcut, and multiply the top equation by -2 to get our new system:
  1. -2x - 4y = -28
  2. 2x + y = 40
Now add both equations together
(-2 _ 2)x (-4 + 1)y = -28 + 40
-3y = 12

To solve this equation, we type it in our search engine and we get:
y = -4

We substitute this back into equation 1 for y = -4:
x + 2(-4) = 14
x - 8 = 14

To solve this equation for x, we type it in our search engine and we get:
x = 22
 
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