A first number plus twice a second number is 5. Twice the first number plus the second totals 19. Find the numbers

A first number plus twice a second number is 5,

This would be x + 2y = 5

Twice the first number plus the second totals 19.

This would be 2x + y = 19

x - x + 2y = 5 - x

2y = 5 - x

2y/2 = 2.5 - 1/2x or y = 2.5 - 0.5x

You cant find the value of the numbers if 2 out of 3 of the numbers are missing.