Whats the solution for 7x−y=7 x+2y=6

Multiply the first equation by 2 to then use elimination by adding the 2 equations.
So, 14x-2y=14
+. x+2y=6

Equals 15x=20 so x=20/15=4/3

Plug in to first equation to get y
7(4/3)-y=7
28/3-y=7
28/3-y=21/3
So y=7/3

Plug both x and y into second equation to check
4/3+2(7/3)=
4/3+14/3=18/3=6 it works

So x=4/3, y=7/3

 -51

Work Shown:

f(x) = -(2x-1)^2 - 2

f(-3) = -(2*(-3)-1)^2 - 2 ... replace every x with -3

f(-3) = -(-6-1)^2 - 2

f(-3) = -(-7)^2 - 2

f(-3) = -49 - 2

f(-3) = -51