f(-3) would be 36.
When looking at synthetic division, the numbers across the top represent the coefficients of x^2, x and the constant in that order. Therefore, the equation is as follows.
2x^2 - 5x + 3
Now we can put -3 into the equation and solve.
2(-3)^2 - 5(-3) + 3
2(9) + 15 + 3
18 + 15 + 3
36