For each systems of equations below choose the best method for solving and solve 3x+y=24 -x-y=-10

Solve the following systems of equations by graphing
$\{\begin{array}{l}-2x+4y=12\\ y=\frac{1}{2}x\end{array}$

Prove that ${\displaystyle f\left(f\left(x\right)\right)\ge 0}$ for all real x

Solve the system of equations by hand.
$\{\begin{array}{l}5x-4y=-5\\ 3x+y=14\end{array}$

with total expenses of $6,390 and take-home pay of $7,450, how much money is left for savings?

A bag contains red and blue marbles. Given that $\frac{17}{20}$ of the marbles are red, what percent of the marbled are blue?

A quadratic equation ${\displaystyle a{x}^2+bx+c=0}$ has equal roots at ${\displaystyle a=2c}$
How could we find the sum of reciprocals of the roots of this equation?

I have this simultaneous equation:
$\{\begin{array}{l}{x}^2-4x+4+y^2-2y+1=9\\ x^2-10x+25+y^2-14y+49=36\end{array}$
How do I solve it?