What would this be as an equation “you earn $0.85 for every cup of hot chocolate you sell. how many cups do you need to sell to earn $55.25? ”

Arandom high school question but a hard one

Which is the graph of the piecewise function f(x)? f(x)=[tex]f(x) = \left \{ {{-x+1, x\leq 0 } \atop {x+1, x\ \textgreater \ 0}} \right.[/tex]

Find the solution of this system of equation -7x+y=-20 9x-3y=36