Me with this! i've been stuck for 20 minutes

The graph represents the gallons of water in a water tank with respect to the number of hours since it was completely filled

What value of x is in the solution set of 4x - 12 s 16 + 8x? -10 -9 -8 -7

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