book Maths Puzzle Numerical Ability

I am not sure how to do this problem because I have no number for a.
8-3x^2=-13
I plugged in my a,b,c for the quadratic formula,but my a was 0. I am not sure how to do this now!

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4+y=12 I really need help please I do not get this problem at all:

The time t in hours, that a storm will last is given by the formula t= square root of d cubed over 216, where d is t