Let
$$int_{0}^{2} f(x) dx = -3, quad int_{0}^{3} f(x) dx = 15, quad int_{0}^{2} g(x) dx = 1, quad int_{2}^{3} g(x) dx = -5,$$
Use these values to evaluate the given definite integrals.
a) $int_{0}^{2} (f(x) + g(x)) dx =$
b) $int_{0}^{3} (f(x) - g(x)) dx =$
c) $int_{2}^{3} (3f(x) + 2g(x)) dx =$
d) Find the value $a$ such that $int_{0}^{3} (af(x) + g(x)) dx = 0.$
$a =$