-3x-5y=-7 -4x+5y=14 solve by elimination

Multiplying an even number of negative numbers gives an answer that is choose from:

What is the value of x in the this question ?

Use the formulas a = x 2 – y 2, b = 2xy, c = x 2 + y 2 to answer this question. one leg of a right triangle has length 11 and all sides are whole numbers. find the lengths of the other two sides. the other leg = a0 and the hypotenuse = a1