Venn Diagram Word Problem

Q:  Superburger sells hamburgers with the choice of ketchup, mustard and relish. One day they sold 256 hamburgers; 140 had mustard, 140 had ketchup, 84 had ketchup and relish, 62 had mustard but no relish, 68 had ketchup and mustard, 38 had all three condiments and 20 had none.

(a) The number sold with relish only is?

(b)The number sold with no relish is?

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OK.  I must redeem myself in the realm of counting!  Too many hasty errors on my last post for discrete math and not enough “thinking.”  Don’t fall victim to this.  And now to the question:

Q:  How many bit strings (reminder: a bit is either 0 or 1) of length 10 have:

(a) Exactly 3 zeros?
(b) Have the same number of 0 and 1
(c) Have at least 7 zeros
(d) Have at least 3 ones?

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