Linear, Quadratic & Polynomial Equation

If (x/y) + (y/x) = √7 then what is the value of (x⁴/y⁴) + (y⁴/x⁴) ?

If x² + 4x + 4 = 0, then the value of x is:

Asad went to the market to buy 12 oranges. But he found that he had the money to buy only 10 oranges. He calculated that if the price per piece of orange was TK. 3 less, he could have bought 12 oranges. How much money did Asad have?