book Maths Puzzle Numerical Ability

solve, using qudratic formula
x(3x+7)-3x=0

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book Other Question

Find two consecutive integers such that the sum of 2 times the first integer and 4 times second integer is 46. I'm not understanding "no solutions" or infinitely many solutions where appropriate...How do I tell the difference?
y = x
y = 3x + 2