1/3y+1/2=2/3 me its solving equations

Which of the following is most likely the next step in the series? a3z, b6y, c9x, d12w, е15v, f18u

To solve the system of equations below, pedro isolated the variable y in the first equation and then substituted it into the second equation. what was the resulting equation? { 5y=10x {x^2+y^2=36

Do you mind if you guys me with this question i’m on number 8