590 favored both
735 favored only capital punishment
950 - 590 = 360 favored only stricter gun control.
Given that, 2000 - (590 + 735 + 360) = 2000 - 1685 = 315 approved of neither.
For b, you need those that favored only capital punishment + both
For c, you need ONLY gun control
For d, as long as one is true, the whole statement is true, so you need people who want gun control, only + people who want capital punishment, only + people who want both
For e, whatever remains must be the answer.