book Maths Puzzle Numerical Ability

This is a problem that I have absolutely no idea how to do it.

Calculate the value of b^2 - 4ac and state how many real solutions the equation has 20x = 4x^2 + 25

Would you

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book Other Question

Could you help me rewrite the expression 2sqrt3+sqrt2/sqrt3-sqrt2 so there are no radicals in the denominator? I guess we could say rationalize the denominator. Thank you so much. Jane is twice as old as Tom. In 8 years their ages will total 70. How old is each now?