Question

A first number plus twice a second number is 9 . Twice the first number plus the second totals 30. Find the numbers.

Answer 1

Explanation:

Let x and y be the numbers;

We have x + 2y = 9 and 2x + y = 21;

Then, x = 9 - 2y;

Finally, 2(9-2y) + y = 21 ;

18 - 4y + y = 21;

18 - 3y = 21;

-3y = 3;

y = - 1;

x = 9 - 2× (-1);

x = 9 + 2 ;

x = 11;