Question 896586
The problem is "that number". 
Does that mean the first number, second number or some sum or product?
I am going to assume it is the second number.

The next question is what is thrice? Just x^2 or ((x^2+5y)
x^2-2xy=-1,
2xy+3*(x^2+5y)=10
x=-2.88161,   y=-1.6143

or 
x^2-2xy=-1,
2xy+3*x^2+5y=10
x=1, y=1