Answer: infinitely many solutions
Explanation: 6y = -3x + 30 rewrites to 3x + 6y = 30
1. align equations x + 2y = 10
3x + 6y = 30
2. multiply first equation by -3 to get -3x - 6y = -30
3. align equations -3x - 6y = -30
3x + 6y = 30
4. add the equations and you they cancel out, which means infinitely many solutions