I would however make two suggestions:
1. Check your final answer by substituting it into the given equations.
2. Multiplying the first equation by 2 and the second by 4 to eliminate x is a bit inefficient. I'd suggest just multiplying the second by 2 .... you'll achieve the same result with less work and therefore more quickly and with less chance of error:
Originally Posted by duckegg but edited (in red) by Mr F